Motor blew up today.....need some tuning experts in here.

[lwrs10]

I have been fighting this weird lean spike issue I have any time my MAP reads above 75KPA. It happens open loop or closed loop, speed density or mass air, every single time it passes the 75KPA point and is held there for longer than 3 seconds. It can be seen with my wideband, and the truck stumbles for a second. It is always followed my a very rich spike. It only happens when it is a steady load, never during a transient. I have a fuel pressure gauge in the truck, and it is always steady during the spikes.


I had the truck on the dyno already, and all I did was roll into the throttle so the lean spike happened before I went WOT. It only happens once everytime you pass the 75KPA mark.


I was finally satisfied with my VE table today, so it took it out of speed density and changed it to MAF only. I added a ton of fuel on the top of the MAF table just to be sure it was not lean. Well I didnt shoot that far off, because the AFR came in pretty much 11.3 stable. Little rich, but something I could work with. But I discovered this lean spike still happens WOT, about 3 seconds after flooring it.


I gave it a few short WOT burst just to make sure my AFR was safe before I slowed down and nailed it.


The lean spike happened to show up right as it shifted into 3rd just a tad over 5 grand....a spike of about 15AFR. Well it popped a piston right there. you can see this happen right about frame 6534. As it shifted, you can see the rpms started to rise, then they slowly started to drop even though I was still WOT. Thats where it started to run on only 7 cylinders.


Here is a screenshot of when it happened...


http://i.imgur.com/rRZPMay.jpg






What in the hell is going on here? Please help me figure this out before I blow up another motor....


*will attach some files when I figure out how*

[Fast355]

I have been fighting this weird lean spike issue I have any time my MAP reads above 75KPA. It happens open loop or closed loop, speed density or mass air, every single time it passes the 75KPA point and is held there for longer than 3 seconds. It can be seen with my wideband, and the truck stumbles for a second. It is always followed my a very rich spike. It only happens when it is a steady load, never during a transient. I have a fuel pressure gauge in the truck, and it is always steady during the spikes.


I had the truck on the dyno already, and all I did was roll into the throttle so the lean spike happened before I went WOT. It only happens once everytime you pass the 75KPA mark.


I was finally satisfied with my VE table today, so it took it out of speed density and changed it to MAF only. I added a ton of fuel on the top of the MAF table just to be sure it was not lean. Well I didnt shoot that far off, because the AFR came in pretty much 11.3 stable. Little rich, but something I could work with. But I discovered this lean spike still happens WOT, about 3 seconds after flooring it.


I gave it a few short WOT burst just to make sure my AFR was safe before I slowed down and nailed it.


The lean spike happened to show up right as it shifted into 3rd just a tad over 5 grand....a spike of about 15AFR. Well it popped a piston right there. you can see this happen right about frame 6534. As it shifted, you can see the rpms started to rise, then they slowly started to drop even though I was still WOT. Thats where it started to run on only 7 cylinders.


Here is a screenshot of when it happened...


http://i.imgur.com/rRZPMay.jpg






What in the hell is going on here? Please help me figure this out before I blow up another motor....


*will attach some files when I figure out how*

I get a small leaner spike from the torque management spark retard, but nothing quite like yours.

[EagleMark]

I was thinking TM too. But can't remember it ever acting this way? Lag, lean then rich?

Can't really think of anything tune related that could do this if VE is dialed in, especially MAP and MAF?

What happens, or happened... if you were running Open Loop?

Bummer on the piston, but I don't think a 15 AFR lean spike during WOT caused it... unless it was some spark knock not being handled properly for a long time? Have you pulled the plugs and looked for specks/fly turds on the plugs?

[mecanicman]

Look at your map signal, and the coresponding drop in cylinder air. Something mechanical was going on, maybe on the cylinder that let go? I added cylinder air in with map and maf and watched them dance with tps reading 100%, looks like an engine issue to me.

[Fast355]

I was thinking TM too. But can't remember it ever acting this way? Lag, lean then rich?

Can't really think of anything tune related that could do this if VE is dialed in, especially MAP and MAF?

What happens, or happened... if you were running Open Loop?

Bummer on the piston, but I don't think a 15 AFR lean spike during WOT caused it... unless it was some spark knock not being handled properly for a long time? Have you pulled the plugs and looked for specks/fly turds on the plugs?

I was thinking it was the van that had the lean spikes on the upshifts but when I looked at some of the old logs, nothing. Then I opened a few early ones on the Titan and low and behold lean spike city. Its MAF only but the torque management timing retard was driving it lean. I simply added fuel in the cells used during the load transition. Worked like a charm.

On the other hand that dual planed dry intake modified for PFI may have some strange resonance or d u namic causing it to starve some cylinder and overfeed another. Nobody really knows without seeing the OEM marine tune. I know when I had TBI on a performer rpm vortec the air/fuel ratio varied substantially cylinder to cylinder with over 200* EGT differences between cylinders. When the intake was flowed it was discovered that the runners do not flow equally at all. Some port matching and grinding helped somewhat.

In my application the crossram L31 marine intake caused the whole tune to richen up with only a little more AE needed.

[lwrs10]

I was thinking TM too. But can't remember it ever acting this way? Lag, lean then rich?

Can't really think of anything tune related that could do this if VE is dialed in, especially MAP and MAF?

What happens, or happened... if you were running Open Loop?

Bummer on the piston, but I don't think a 15 AFR lean spike during WOT caused it... unless it was some spark knock not being handled properly for a long time? Have you pulled the plugs and looked for specks/fly turds on the plugs?



Torque management is zero'd out in my tune, so not sure on that. I have ran it full open loop and it will still do it. Does not have to be WOT, it will do it anytime it is above 75kpa, and held there at a steady rate for 3 seconds.

I have even jumpered off an injector and hooked a portable oscope up to it in the cab, and the injectors just shut completely off when these lean spikes happen. So i would 100% say it is the computer causing it. Why.....i have no idea. That is why I am here.




Look at your map signal, and the coresponding drop in cylinder air. Something mechanical was going on, maybe on the cylinder that let go? I added cylinder air in with map and maf and watched them dance with tps reading 100%, looks like an engine issue to me.

That was when it shifted into 3rd, so i would expect a slight dip in the MAP reading. I can post screenshots of this happening hundreds of other times not during a shift and the MAP kpa does not move.

[mecanicman]

From looking at the different logs you posted, I can see this stuff in everyone. Your koeo map value is 102kpa. You never hit that going wot, best I believe I saw was 98kpa. Is your air filter to small, or you have silicone elbow you are sucking shut? You have a map sensor "tick" in your steady state cruise with no tps fluctuation. Something was up with the engine. I have included 2 pics from your logs that are not shifts, and show the same thing I described before. Map sensor doing the funky chicken. Your issue is not tune related.

[EagleMark]

Nice use of scanner! :thumbsup:

Could that be a intake valve? Lean pop?

[mecanicman]

I would lean towards valvetrain related, but with just the log its hard to pinpoint.

[lwrs10]

I need to post some screenshots of this lean spike when not WOT.

as far as the MAP sensor varying at WOT, what would cause that? Truck ran perfect everywhere else but that lean spike. I do have some logs from when the engine was bone stock, so I will compare those.

[lwrs10]

Here is that lean spike when not WOT. You can see everything is steady as can be when it happens. I have even hooked an oscope up to an injector, ran a jumper into the cab, and monitored the pulsewidths in real time. The injectors shut off for 300ms completely everytime this happens. I have also monitored voltage on the positive side of the injector plug, and it does not drop at all.

I am 100% sure this is related to the WOT spike, and 100% sure it is a computer related issue since I can see it stop commanding the injectors when it happens.

http://i.imgur.com/WW1WWh5.jpg

http://i.imgur.com/eJuH8Qn.jpg

[mecanicman]

Email me the log you posted, I'll on my address.

[Caleditor]

I was under the impression the lean spike was caused from "Fuel during A/F transition period 1 to cause a lean state".

[lwrs10]

I was under the impression the lean spike was caused from "Fuel during A/F transition period 1 to cause a lean state".

I hope it is too.


And.....looks like a valvespring broke, and the lean spike was not the root cause. Dropped #5 intake valve. Took the valve cover off and noticed the spring and locks/retainer just laying there. Took the drivers side head off and looks like pieces of the #5 made it back into the intake and took out all the other holes too. Even the passenger side spark plugs are all bent up.

[mecanicman]

The valve spring explains your map signal. Have pic of the engine bay before you took it apart? Still like to see that log.

[EagleMark]

I agree. I think your valve spring was broke causing this issue long before everything came flying apart.

Log pictures clearly show it was not a transition issue.

[lwrs10]

The valve spring explains your map signal. Have pic of the engine bay before you took it apart? Still like to see that log.

still trying to wrap my head around what you are getting at with the map signal. It went all the way back to october of last year through my logs when my engine was completely stock. The MAP looks EXACTLY like it does now. And it ran great then. Same tiny little dips WOT, same max KPA, etc. And the only thing common between the current motor was the shortblock. Let me post some pics....

[Caleditor]

still trying to wrap my head around what you are getting at with the map signal. It went all the way back to october of last year through my logs when my engine was completely stock. The MAP looks EXACTLY like it does now. And it ran great then. Same tiny little dips WOT, same max KPA, etc. And the only thing common between the current motor was the shortblock. Let me post some pics....
And you could see that the AFT1 flag had just run

[lwrs10]

And you could see that the AFT1 flag had just run

there is that too.

we can throw out the WOT stuff, because I had a mechanical failure. But....gotta get rid of this lean then rich spike at part throttle once i fire up the new engine this weekend.

and dammit....I do not have any pics of it. I have half completed pics.

http://i.imgur.com/0zqj6Fr.jpg

[mecanicman]

Broken valve springs cause cylinder missfires which can show up on wideband as lean. You may still have another problem, I would still like to see the log you referanced above. Just checked out your build thread on s10 forum. I have 3 s10s, here is the link to my turbo project if your interested. http://www.s10forum.com/forum/f213/just-another-800rwhp-daily-i-hope-503806/

[lwrs10]

Not sure a broken valve spring would make both banks go lean at the same time though.

[mecanicman]

What injectors are you running?

And both banks is a valid point that there is another issue at work. Now if only I could see this issue..................lol

[lwrs10]

What injectors are you running?

And both banks is a valid point that there is another issue at work. Now if only I could see this issue..................lol

Which log would you like to see exactly?

And I am running the LS3 injectors.

[mecanicman]

I want to see a log with a good capture of your lean/rich spike. And your injector data is way wrong, which may be contributing to the spike. Unfortunately I'm back to work today, but I'll get you the data in the correct format tonight.

[lwrs10]

Injector data is wrong? Fuel pressure is 58 psi, and the flow rate is 41.7lb/hr at that pressure.

The offsets are derived from the stock LS3 tune, using the 400 column, which is equal to the 0 kpa line in our tune. The IFR and offsets are flat across because I am using a return style system.

The short pulse adder is also straight out of the LS3 tune, but interpolated for the 0411 values, as are short pulse limit and minimum pulse width.

But I am interested to see what you have. I find it very hard to believe stock GM data for a stock GM injector is wrong.

[mecanicman]

If you have all the answers why are you asking for help? I dont need to keep arguing with you. I can promise that using ls3 injector data does not result in negative short pulse adder values like you have, or a table the looks anything like that. Good luck with your tune.:mad1:

[lwrs10]

If you have all the answers why are you asking for help? I dont need to keep arguing with you. I can promise that using ls3 injector data does not result in negative short pulse adder values like you have, or a table the looks anything like that. Good luck with your tune.:mad1:

I am in no way trying to argue. I can post a stock ls3 tune that has those negative short pulse adders. And as I said before, I would like to see the data you have.

My apologies for making you mad...totally not my intention.

[EagleMark]

Listen guys, there's never been arguing here! Maybe difference of opinions/knowledge or facts? But we just talk about it and come to a conclusion! :thumbsup:

mecanicman has been asking for data logs and none posted yet? He seems more then willing to help and has some knowledge I'd like to hear as well! Maybe if he had them this difference could have been answered already?

Maybe it's my fault as your first post said
*will attach some files when I figure out how* So when you click Reply to post, look underneath and click Go Advanced, then under that box is the attatchement manager and you can upload your files. I'm not sure all HP Tuners file extensions have been added so if you have a problem let me know what the extensions are and I will add them. For now you could just zip the files.

[lwrs10]

I will post some logs in a few minutes. I stayed up all night swapping in the other motor I had and drove it to work today. No way for me to post logs from work, as I do most of my posting from my phone. That should explain the delay in those logs.

BTW, it did the same exact thing with this "new" motor. I looked through the tune to see if I missed anything when I changed most things back to stock. Found I missed the injector timing, and the new motor has a stock cam. Set the EOIT to match what I had in there, which was to start when the exhaust valve closed. That lean spike went away completly until I made an idle airflow change and it came back. Then I set the EOIT back to the stock numbers and viola! No more massive lean spike.

Once I get my heads back together and swap the valvetrain over to the new motor, I have a damn good lead on how to fix it!

[lwrs10]

here is a log with some pretty distinct spikes. One happens about frame 3850.

https://docs.google.com/file/d/0B4qslwsH0IjsUk9SSTRXY3RPSlU/edit?usp=sharing

Here is a 2010 Camaro SS LS3 bone stock injector data screenshot. This is exactly what my injectors came out of. These PCM's work off pressure delta, but to figure out what to use for an 0411 with a return style fuel system, you simply find your fuel pressure number in those numbers and use it. The pressure delta at 58 PSI rail pressure would simply be 58 for 0KPA. So pretty easy to do. I also have this data in E67 format too that uses the 400 scale.

Most of the short pulse adder table is negative because of the non linearity of these below 4ms pulse width. They actually have an upward swing from the linear flow line right below 4ms....hence the negative number to reduce fuel. Just below 1ms pulse width is where the flow falls off, and thats where the numbers go positive.

http://i.imgur.com/860NduA.jpg




And here is the short pulse adder table side by side with mine. Surprisingly the 0411 has more resolution.

http://i.imgur.com/PnYAhPG.jpg

[Fast355]

I am not sure what mechanicman is getting at with the MAF and MAP signals. I have never tuned an engine with a stock throttle body or an air cleaner that did not drop below baro as the rpm climbed nor have I tuned any engine that had steady maf/map signals. They ALL bounce. Dodge 4.7/5.7/5.9, GM TBI, TPI, LT1, Vortec, LS1, 3100, 3400, and even my 2012 Titan thats been tuned since 2,000 miles. Gotta remember the engine runs in big pulses as the various valve open and close and the sensor reading multiple times a second record thes pulses.

I would be more inclined to believe he has an issue in the VE table thats causing the PCM to run lean after AE times out. It also helps to bring PE in sooner than the OE 90% and bypass the delay by lowering the delay rpm.

[mecanicman]

My responce seemed more justified at the time, I had a rough day at work. I find it very frustrating when someone asks for help, then discounts everything you say. My patience was thin and for that I appologize.

I have not been on as my primary computer, the one I do all my tuning with, died. I have lost huge amounts of data and am still stuggling to piece it back together.

[mecanicman]

I am not sure what mechanicman is getting at with the MAF and MAP signals. I have never tuned an engine with a stock throttle body or an air cleaner that did not drop below baro as the rpm climbed nor have I tuned any engine that had steady maf/map signals. They ALL bounce. Dodge 4.7/5.7/5.9, GM TBI, TPI, LT1, Vortec, LS1, 3100, 3400, and even my 2012 Titan thats been tuned since 2,000 miles. Gotta remember the engine runs in big pulses as the various valve open and close and the sensor reading multiple times a second record thes pulses.

I would be more inclined to believe he has an issue in the VE table thats causing the PCM to run lean after AE times out. It also helps to bring PE in sooner than the OE 90% and bypass the delay by lowering the delay rpm.

Every engine is a little different, some dance more then others. But I believe I do a lot more tuning then most of you as I run it as a buisness locally and do it remotely as well. I see more logs then the average person and have a trained eye for it. I am not trying to brag, but you didnt find it strange I predicted valve train problems and then shortly after it was posted a failed valve spring was the cause? Because I have seen it before, its subtle but its there.


My collection of logs was lost recently, so this is the best example I could find. This is a stock l76 with a mild cam, so not drasticly different from what the s10 is running. You can see there is a 1 kpa variation but overal pretty smooth.
http://imageshack.us/a/img716/866/0e3r.jpg

The same example I posted before, you can see its more jagged and has a lot more variance to it.
http://imageshack.us/a/img33/3899/tgd3.jpg

This was what stood out to me at first, I can see now with the logs there is another problem present, but this is what killed the engine, not the lean spike.

[mecanicman]

From the log you posted I can see its not the injector data causings your lean issue, may be the cause of your "shark fin". I dont agree with the negative portion of the short pulse adder table, but thats another story I dont feel like getting into right now. Your lean spike happens above any pulse width the short pulse adder will effect.

Perhaps try a different file when the engine is up and running? I can modify an express van file for you, have used it before on the same swap without issue.

[lwrs10]

Finally some time to reply...

Finished up swapping the engine out. Bone stock motor with the same intake and injectors. Still had the lean spike and still had the big KPA fluctuations. Looking through my tune I noticed I forgot to change my injector timing back to stock, as it was changed to match my cam values. Changed it back to stock and BLAMMO! No more lean spike. I tested it at least 20 times, and I am 100% sure injector timing was the issue. I can change it and make the lean spike happen, change it back no spike. So glad I got that ironed out.

But the KPA dance was still there. On a bone stock motor. Not a single part in the valvetrain was common between motors. So on a longshot i tried something.

Here is my stock V6 air intake on that V8 motor, with a stock intake. It does have the V8 MAF and tube, but that is the V6 hat. I started looking at this because my WOT KPA indicated a restriction somewhere.

http://i.imgur.com/xGbulFll.jpg


So on a drunken escapade I grafted an 03 Cobra JLT intake I had laying around as a spare to fit this truck. This is a 4" cold air. And I had the BIG 5 wire MAF laying around from my LS swapped S10 blazer that blew up due to a lifter failure.

Here is what I came up with:

http://i.imgur.com/bV4kWcsl.jpg

And holy hell.....what a difference it made. I now hover around 100kpa WOT. Truck feels a lot more powerful, gas mileage went up damn near 8mpg, and everything ironed itself out I was having problems with.

I swapped my cam and fixed heads back on it yesterday and truck runs great. Absolutely a totally different engine now. I rented an hour of dyno time today and it put down some damn good numbers too. 389hp/422tq, and those are corrected numbers on a dynojet.

So moral of the story is dont screw with the injector timing on these motors, and do not run cheap valve springs. Causes weeks worth of headaches.

[Fast355]

Finally some time to reply...

Finished up swapping the engine out. Bone stock motor with the same intake and injectors. Still had the lean spike and still had the big KPA fluctuations. Looking through my tune I noticed I forgot to change my injector timing back to stock, as it was changed to match my cam values. Changed it back to stock and BLAMMO! No more lean spike. I tested it at least 20 times, and I am 100% sure injector timing was the issue. I can change it and make the lean spike happen, change it back no spike. So glad I got that ironed out.

But the KPA dance was still there. On a bone stock motor. Not a single part in the valvetrain was common between motors. So on a longshot i tried something.

Here is my stock V6 air intake on that V8 motor, with a stock intake. It does have the V8 MAF and tube, but that is the V6 hat. I started looking at this because my WOT KPA indicated a restriction somewhere.

http://i.imgur.com/xGbulFll.jpg


So on a drunken escapade I grafted an 03 Cobra JLT intake I had laying around as a spare to fit this truck. This is a 4" cold air. And I had the BIG 5 wire MAF laying around from my LS swapped S10 blazer that blew up due to a lifter failure.

Here is what I came up with:

http://i.imgur.com/bV4kWcsl.jpg

And holy hell.....what a difference it made. I now hover around 100kpa WOT. Truck feels a lot more powerful, gas mileage went up damn near 8mpg, and everything ironed itself out I was having problems with.

I swapped my cam and fixed heads back on it yesterday and truck runs great. Absolutely a totally different engine now. I rented an hour of dyno time today and it put down some damn good numbers too. 389hp/422tq, and those are corrected numbers on a dynojet.

So moral of the story is dont screw with the injector timing on these motors, and do not run cheap valve springs. Causes weeks worth of headaches.

My injector timing has been changed and it runs GREAT. Just do not run more than 6.5 as that coincides near to BDC. My issue with the lean spike was the PE RPM delay being set at 2,000 rpm, which was overlapping the stall speed.

[lwrs10]

My injector timing has been changed and it runs GREAT. Just do not run more than 6.5 as that coincides near to BDC. My issue with the lean spike was the PE RPM delay being set at 2,000 rpm, which was overlapping the stall speed.


mine was at 6.86.

[Fast355]

Every engine is a little different, some dance more then others. But I believe I do a lot more tuning then most of you as I run it as a buisness locally and do it remotely as well. I see more logs then the average person and have a trained eye for it. I am not trying to brag, but you didnt find it strange I predicted valve train problems and then shortly after it was posted a failed valve spring was the cause? Because I have seen it before, its subtle but its there.

My collection of logs was lost recently, so this is the best example I could find. This is a stock l76 with a mild cam, so not drasticly different from what the s10 is running. You can see there is a 1 kpa variation but overal pretty smooth.

The same example I posted before, you can see its more jagged and has a lot more variance to iThis was what stood out to me at first, I can see now with the logs there is another problem present, but this is what killed the engine, not the lean spike.

You are comparing a WOT and a part-throttle log. Two different beasts

Attached are 3 different vehicles. My Express, my 2012 Titan, and a 4.8. Every last one has a rough MAF signal at WOT and yet all run well.

[mecanicman]

You are comparing a WOT and a part-throttle log. Two different beasts.

TPS is 100% in both, and you can see it other places.

[mecanicman]

Finally some time to reply...

Finished up swapping the engine out. Bone stock motor with the same intake and injectors. Still had the lean spike and still had the big KPA fluctuations. Looking through my tune I noticed I forgot to change my injector timing back to stock, as it was changed to match my cam values. Changed it back to stock and BLAMMO! No more lean spike. I tested it at least 20 times, and I am 100% sure injector timing was the issue. I can change it and make the lean spike happen, change it back no spike. So glad I got that ironed out.

But the KPA dance was still there. On a bone stock motor. Not a single part in the valvetrain was common between motors. So on a longshot i tried something.

Here is my stock V6 air intake on that V8 motor, with a stock intake. It does have the V8 MAF and tube, but that is the V6 hat. I started looking at this because my WOT KPA indicated a restriction somewhere.

http://i.imgur.com/xGbulFll.jpg


So on a drunken escapade I grafted an 03 Cobra JLT intake I had laying around as a spare to fit this truck. This is a 4" cold air. And I had the BIG 5 wire MAF laying around from my LS swapped S10 blazer that blew up due to a lifter failure.

Here is what I came up with:

http://i.imgur.com/bV4kWcsl.jpg

And holy hell.....what a difference it made. I now hover around 100kpa WOT. Truck feels a lot more powerful, gas mileage went up damn near 8mpg, and everything ironed itself out I was having problems with.

I swapped my cam and fixed heads back on it yesterday and truck runs great. Absolutely a totally different engine now. I rented an hour of dyno time today and it put down some damn good numbers too. 389hp/422tq, and those are corrected numbers on a dynojet.

So moral of the story is dont screw with the injector timing on these motors, and do not run cheap valve springs. Causes weeks worth of headaches.


Glad you got it sorted. Nice numbers our of mostly stock vortec 5.7.

[Fast355]

TPS is 100% in both, and you can see it other places.

What I was getting at is the first log was at WOT the whole log and the 2nd for only a brief period. That being said I would expect a 6.2 with variable cam timing to have a smoother MAP/MAF signal than the older engine. It has a larger throttle body, larger intake ducting, higher flowing intake, etc.

I am wondering if I could even get a 3" elbow like that above my throttle body, much less a 4".

[mecanicman]

What I was getting at is the first log was at WOT the whole log and the 2nd for only a brief period. That being said I would expect a 6.2 with variable cam timing to have a smoother MAP/MAF signal than the older engine. It has a larger throttle body, larger intake ducting, higher flowing intake, etc.

I am wondering if I could even get a 3" elbow like that above my throttle body, much less a 4".

L76 is 6.0, that one is variable cam timing and dod delete running a lingenfelter converter box and 0411 pcm. Has a stock car intake with an ebay adapter plate for a stock 85mm truck throttle body, a marginally larger version that is the same as whats on the vortec 5.7.(i have actually put the 85mm on 4.3 buy changing the shaft so pulls the right way and some very slight grinding). Cam is 230/238 .600”/.604. Engine currently resides in a 1990 silvia running 11.30's with traction issues.

I may not have been as right as I thought I was about the valve spring, but I bet if he posted a log of the same situation you are calling part throttle now it would be a lot smoother. It was likely the valve spring causing the steady state cruise tick and the intake setup causing the wot dance. Either way I wouldnt consider it normal.

[Fast355]

L76 is 6.0, that one is variable cam timing and dod delete running a lingenfelter converter box and 0411 pcm. Has a stock car intake with an ebay adapter plate for a stock 85mm truck throttle body, a marginally larger version that is the same as whats on the vortec 5.7.(i have actually put the 85mm on 4.3 buy changing the shaft so pulls the right way and some very slight grinding)..

I am fairly certain the WOT dance you are seeing in all of my logs is the restrictive intake designs on the engines I am tuning. My Titan only has a 74mm TB or close. The Express has the restrictive elbow in place. The 4.8 has a stock throttle body as well. I wish it would end up closer to the 99-100 KPA baro pressure, but it falls where it falls at the moment.

I am actually running the L31 marine intake now and could probably step up to an 85mm LS TB with a little rework and could possibly get a 3" short radius elbow on top, but there is not much room there.

The Titan has a 4" CAI on it at the moment, but it necks down to smaller than 3" at the intake coupler.

I am waiting to see the results of a project being performed by a Titantalk member. Basically he had a big LS intake porting shop graft a LS2/LS3 intake flange and LS2/LS7 throttle body to a 2007+ Titan intake manifold and built a true sleeveless 4" CAI.

[lwrs10]

L76 is 6.0, that one is variable cam timing and dod delete running a lingenfelter converter box and 0411 pcm. Has a stock car intake with an ebay adapter plate for a stock 85mm truck throttle body, a marginally larger version that is the same as whats on the vortec 5.7.(i have actually put the 85mm on 4.3 buy changing the shaft so pulls the right way and some very slight grinding). Cam is 230/238 .600”/.604. Engine currently resides in a 1990 silvia running 11.30's with traction issues.

I may not have been as right as I thought I was about the valve spring, but I bet if he posted a log of the same situation you are calling part throttle now it would be a lot smoother. It was likely the valve spring causing the steady state cruise tick and the intake setup causing the wot dance. Either way I wouldnt consider it normal.

The 5.7 and 4.3 throttle bodys are the exact same, except for the throttle shaft and blade, and are both 70mm. The one on my truck is a 76mm from a marine engine. I would be very interested in this 85mm one you are talking about. What did it come off of?

[mecanicman]

The ls engines use the same throttle body. There are some differances, but if you have one of each type you can swap the pieces to make it work. The 6.0 is supposed to be 85mm, I think I measured it less then that but was bigger then what I had. Mostly is swapping the shaft cause they pull different ways. Some have vacume tubes that stick out and interfere. I had a collection of both and was able to make one that worked. I think I used a cutoff wheel to extend shaft opening for blade just slightly. I had to grind the stock plastic intake to make it work.

[Fast355]

The ls engines use the same throttle body. There are some differances, but if you have one of each type you can swap the pieces to make it work. The 6.0 is supposed to be 85mm, I think I measured it less then that but was bigger then what I had. Mostly is swapping the shaft cause they pull different ways. Some have vacume tubes that stick out and interfere. I had a collection of both and was able to make one that worked. I think I used a cutoff wheel to extend shaft opening for blade just slightly. I had to grind the stock plastic intake to make it work.

Yea they share the same bolt-pattern for sure. I am still tossing around the idea of converting the Express to a 24x crank sensor, CNP and DBW when I pull the 350 and build a 383 or 396. Thinking it would not be hard to integrate traction control and cruise control into the setup without any additional mechanical components. The 350 already loves to blow the tires away in the rain even from a roll and I know more power is just going to make it worse.