1993 Camaro LT1 Tuning

Hi everyone. I'm a lubrication guru looking to get into tuning for my own car. I'm very green when it comes to this so bear with me. My previous experience with tuning is with carburetors so this is all new.

What I know...
- It uses a chip.
- It's speed density.
- Has the opti-spark.

This engine just has a bolt-ons with a canned tune. It's 100% track only as a bracket car. It's fairly consistent as it is aside from the fuel. I'm having inconsistency issues from one batch of pump fuel to another (different specific gravity and ethanol content) which is throwing off my predictability and forcing me to relearn the car every time I fill it up. I'm looking to convert to E85 (VP X85 or C85) for not only more consistency from one tank to another, but more consistent overall with the ethanol. I'm upgrading the fuel pump and injectors for this. That will of course require tuning.

I don't need real time tuning, I don't think. I would like to datalog a 1/4-mile pass and then be able to make adjustments and burn a new chip based on that pass. I think that's how it works. lol

Any advice for a newb is appreciated. Which burner? What software? Thanks in advance.

EDIT: I plan to delete the O2 sensors and run only on open loop.

ah super easy. i use a minipro from ebay on the cheap and it's worked great but you can go ahead and get something from moates.net if you want. get a few (i think) 29c256 chips and don't write over your original, that way no risk.

get the original bin from the original chip using your chip burner,

get tunerpro (free)

get an XDF file from here

http://www.gearhead-efi.com/Fuel-Inj...mation-DA2-DA3

load bin and xdf

make changes

burn new bin

swap chip

if you need to do LOTS of tuning which would involve taking the chip in and out a hundred times, then use an emulator and/or a zif socket so you don't end up breaking something

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Originally Posted by steveo

ah super easy. i use a minipro from ebay on the cheap and it's worked great but you can go ahead and get something from moates.net if you want. get a few (i think) 29c256 chips and don't write over your original, that way no risk.

get the original bin from the original chip using your chip burner,

get tunerpro (free)

get an XDF file from here

http://www.gearhead-efi.com/Fuel-Inj...mation-DA2-DA3

load bin and xdf

make changes

burn new bin

swap chip

if you need to do LOTS of tuning which would involve taking the chip in and out a hundred times, then use an emulator and/or a zif socket so you don't end up breaking something

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Steveo, thanks a lot for the help. So it seems pretty straight forward.

Correct me if I'm wrong here. From what I gather, if I was looking to convert this stock LT1 over to VP-X85 fuel with a 255 lph pump and 36 lb/hr injectors while keeping the stock VE tables (since airflow isn't changing) and 43.5 psi fuel pressure... I would simply go in TunerPro and change the fuel flow rate to 36 lb/hr, change the stoich AFR to 9.81 (for VP X85), and then adjust the PE enrichment as necessary?

Injector changes typically require changing flow rate, transient tuning (acceleration enrichment and deceleration enleanment), and injector corrections (voltage and small pulsewidth) at a minimum. In some calibrations you must fine tune single-fire to double-fire transitions for best low rpm operation. Changing fuel type requires changing stoichiometric AFR, power enrichment AFR, and cold engine tuning if desired. Changing fuel also typically requires adjustments to spark timing due to combustion characteristics of new fuel.

just out of curiosity, is E85 really that much more consistent? i was under the impression that E85 is almost never actually 85% ethanol... and the gas it's mixed with is the same inconsistent stuff that you get from the pump anyway, isn't it? i've heard that it's like 50-80% at most pumps because the only vehicles built for E85 are all 'flex fuel' anyway so the exact ratio doesn't matter

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Originally Posted by 1project2many

Injector changes typically require changing flow rate, transient tuning (acceleration enrichment and deceleration enleanment), and injector corrections (voltage and small pulsewidth) at a minimum. In some calibrations you must fine tune single-fire to double-fire transitions for best low rpm operation. Changing fuel type requires changing stoichiometric AFR, power enrichment AFR, and cold engine tuning if desired. Changing fuel also typically requires adjustments to spark timing due to combustion characteristics of new fuel.

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Got it. I'm going to research the effect of each of those parameters and the manner in which they should be altered. Any links would be appreciated.

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Originally Posted by steveo

just out of curiosity, is E85 really that much more consistent? i was under the impression that E85 is almost never actually 85% ethanol... and the gas it's mixed with is the same inconsistent stuff that you get from the pump anyway, isn't it? i've heard that it's like 50-80% at most pumps because the only vehicles built for E85 are all 'flex fuel' anyway so the exact ratio doesn't matter

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That's why I'm using VP Racing's X85 which is a consistent 85% ethanol to 15% gasoline every batch. The car is strictly a track only bracket car so being able to run the same elapsed time consistently round after round is vital. Ethanol is highly oxygenated (VP-X85 is 30.3% oxygen) and has a much lower boiling point of 173*F compared to 380+*F for gasoline. This allows it to flash to vapor quickly in the cylinder and create its own atmosphere for combustion that's less effected by atmospheric conditions. So if the weather changes from one round to another, I won't have to be as concerned about changing the elapsed time or changing the tune. The car is pretty much going to run the same number. (all else equal) From the points series last year, 4 of the top 5 in points were running either E85 or E98 with the one gas burner coming in 4th.

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Got it. I'm going to research the effect of each of those parameters and the manner in which they should be altered. Any links would be appreciated.

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Transients such as sudden throttle angle change or load change affect manifold air density. The purpose of the transient tables is to instigate a rapid change in fueling to maintain the manifold AFR outside the speed density calculation. Goals for acceleration enrichment are to create a mixture to promote best acceleration while staying rich enough to prevent flash combustion and resultant backfire. Most of this tuning is accomplished through iteration testing but generally I would not be surprised if you need to deliver more fuel to the manifold than the injector change alone provides. As a track-only vehicle I would abstain from deceleration enleanment tuning unless the car behaves obnoxiously at the end of the track or as the engine winds down.

Values such as stoichiometric afr, fuel flow rate, and the injector corrections should be populated from provided data. Guesswork always leads to inconsistent tuning although with enough time and determination a calibration can be made to work with incorrect values. Injector corrections and the single-fire to double-fire transition are more likely to play a part at idle or during deceleration. They can greatly affect streetability but as a track vehicle your car may seem fine with minimal work in these areas. Power enrichment AFR can be mapped to power valve operation on a carburetor equipped vehicle. this value should initially be set at the correct AFR for best power for your fuel but should be adjusted based on performance.

Will you be using a WBO2 to help tuning?

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Originally Posted by 1project2many

Transients such as sudden throttle angle change or load change affect manifold air density. The purpose of the transient tables is to instigate a rapid change in fueling to maintain the manifold AFR outside the speed density calculation. Goals for acceleration enrichment are to create a mixture to promote best acceleration while staying rich enough to prevent flash combustion and resultant backfire. Most of this tuning is accomplished through iteration testing but generally I would not be surprised if you need to deliver more fuel to the manifold than the injector change alone provides. As a track-only vehicle I would abstain from deceleration enleanment tuning unless the car behaves obnoxiously at the end of the track or as the engine winds down.

Values such as stoichiometric afr, fuel flow rate, and the injector corrections should be populated from provided data. Guesswork always leads to inconsistent tuning although with enough time and determination a calibration can be made to work with incorrect values. Injector corrections and the single-fire to double-fire transition are more likely to play a part at idle or during deceleration. They can greatly affect streetability but as a track vehicle your car may seem fine with minimal work in these areas. Power enrichment AFR can be mapped to power valve operation on a carburetor equipped vehicle. this value should initially be set at the correct AFR for best power for your fuel but should be adjusted based on performance.

Will you be using a WBO2 to help tuning?

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Thank you for the information. Does this make a difference between batchfire (93) and sequential (94 and later)?

As soon as I cross the finish, I bump the car into neutral to coast off the end of the track. It will see some light part throttle driving just getting down the return road and putting around the pits to the staging lanes, but not enough to warrant keeping closed loop I don't think.

I have an AEM UEGO wideband and monitor coolant, oil, and trans temps closely as I like to stage within a set temp range for each.

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Originally Posted by Polyalphaolefin

Thank you for the information. Does this make a difference between batchfire (93) and sequential (94 and later)?

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My understanding is that 94 and later 8051 ecms calculate acceleration enrichment dynamically. The 92-93 cars have more traditional code which monitor throttle angle and / or load changes to trigger additional injector pulses.

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As soon as I cross the finish, I bump the car into neutral to coast off the end of the track. It will see some light part throttle driving just getting down the return road and putting around the pits to the staging lanes, but not enough to warrant keeping closed loop I don't think.

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I agree. Closed loop operation would likely add more complexity than necessary.

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I have an AEM UEGO wideband and monitor coolant, oil, and trans temps closely as I like to stage within a set temp range for each.

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If you monitor oil temp then you have a great tool for helping tune spark advance. Seeing engine knock in a log gives an indication that timing is substantially early. reduced response and higher EGT indicate late timing. But there is a range of timing settings through which spark timing changes do little for EGT or response. Oil temperature tells us a better story. If timing is too early by a few degrees the oil temp will begin to increase under load or acceleration. If you can log oil temp along with load, speed, and spark advance you may be able to dial in spark advance with a greater "degree" of confidence. If you are using an eprom emulator then you can change advance easily between runs while monitoring oil temperature.

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Originally Posted by 1project2many

My understanding is that 94 and later 8051 ecms calculate acceleration enrichment dynamically. The 92-93 cars have more traditional code which monitor throttle angle and / or load changes to trigger additional injector pulses.



I agree. Closed loop operation would likely add more complexity than necessary.



If you monitor oil temp then you have a great tool for helping tune spark advance. Seeing engine knock in a log gives an indication that timing is substantially early. reduced response and higher EGT indicate late timing. But there is a range of timing settings through which spark timing changes do little for EGT or response. Oil temperature tells us a better story. If timing is too early by a few degrees the oil temp will begin to increase under load or acceleration. If you can log oil temp along with load, speed, and spark advance you may be able to dial in spark advance with a greater "degree" of confidence. If you are using an eprom emulator then you can change advance easily between runs while monitoring oil temperature.

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Yep. As an oil guru, I've seen a lot of that happening, but there's also different variables at play there also. For example, an oil with a higher pressure-viscosity coefficient will increase hydrodynamic friction in the bearings at WOT, increasing oil temp more than usual. This is common in nitrous engines where the bottom end is subjected to a lot of shock loading.

I adjust my idle time in the staging lane and time I take to stage in order to get the temps within these ranges.

Coolant: 165-170*F (160*F stat), rises to ~175*F by the end of the run.
Oil: 170-175*F, rises to ~190*F.
Trans: 160-170*F, rises to ~200*F.

It has a TH350 in it with a 9" 4000 stall so I guess I'm not concerned with anything below 4000 rpm. I 2-step to 2000 rpm and then flash the converter from there. It flashes to 4100 rpm, shifts 1-2 at 5400 rpm, falls to 4400 rpm, shift 2-3 at 5300 rpm, and falls to 4500 rpm, crossing the line at 5350 rpm in 3rd.

Given that information, would changing the spark advance at 1000-4000 rpm effect how hard the engine may flash the converter or response in doing so? What I mean is the free rev of the engine from the time I let off the 2-step / brake to when it jumps to the flash rpm if more spark advance would make it respond faster and rev up faster to that rpm, thus (in theory) hitting the converter sooner and harder.

Also, for idle timing. My last car was a carb'd SBF 347ci and it liked ~30 degrees at idle. It idled smoother and cooler with that much advance. Looking at the stock bin file, it seems the LT1 is 25 degrees at 800 rpm. Is there any advantage to increasing that to 28-30 degrees?

I really appreciate all of the advice you and steve have given me.

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As an oil guru, I've seen a lot of that happening, but there's also different variables at play there also. For example, an oil with a higher pressure-viscosity coefficient will increase hydrodynamic friction in the bearings at WOT, increasing oil temp more than usual. This is common in nitrous engines where the bottom end is subjected to a lot of shock loading.

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Interesting. So just how often does the tuner using nitrous recognize that his oil has just saved his bottom (end)?

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would changing the spark advance at 1000-4000 rpm effect how hard the engine may flash the converter or response in doing so?

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If you can produce greater power then you will decrease the response time between stages. That may feel like a harder hit. If you can increase torque production the engine will apply more force to the driveline as the converter flashes which would flash the converter at higher rpm. That may feel like a harder hit.

Is altering the spark timing the best way to do this?

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Looking at the stock bin file, it seems the LT1 is 25 degrees at 800 rpm. Is there any advantage to increasing that to 28-30 degrees?

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I am far from expert when it comes to LT1 tuning. Hopefully someone here can help with specific suggestions for your engine. I know that LT1 and cousin L31 both have combustion chambers designed to promote faster combustion. L31 engines generally require less timing than previous design engines to produce the same power. IIRC the LT1 engines are more forgiving of excess spark advance due to reverse flow cooling and they often tolerate a beginner's eager attempts to find best power when another engine may not. Generally, racing fuel having higher octane and a consistent blend with fewer light end HC's tends to produce more power than pump gas if spark advance is increased over stock settings. But some calibrations use a combination of advance tables designed around good fuel and aggressive knock retard which effectively reduces timing for poor fuel. The goal IMO is to observe and evaluate before jumping in to make too many changes. Luckily bracket racing rewards careful and consistent work.

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Originally Posted by 1project2many

Interesting. So just how often does the tuner using nitrous recognize that his oil has just saved his bottom (end)?

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The best way I've observed to tune a nitrous engine is with EGTs. The oil / bottom end is where I tend to come in. I can cut open the filter to see if there's any particles in there. I also sample the oil and run it through ICP-AES and FTIR analysis. What I'm usually looking for is lead and copper which would indicate excessive bearing wear. Aluminum can show up with some bearings, but that's rare. The ideal oil is calculated beforehand with the expected cylinder pressure, shock, rpm, bearing clearance, oil temp, etc... I wouldn't advise the same oil for a nitrous engine as I would a turbo or supercharged engine, even if both made similar power at similar rpm with similar peak cylinder pressures.

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Originally Posted by 1project2many

If you can produce greater power then you will decrease the response time between stages. That may feel like a harder hit. If you can increase torque production the engine will apply more force to the driveline as the converter flashes which would flash the converter at higher rpm. That may feel like a harder hit.

Is altering the spark timing the best way to do this?

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That I'm not sure. I would have to experiment, I suppose. I imagine I could lean it out a bit through that range since the load is low.

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Originally Posted by 1project2many

I am far from expert when it comes to LT1 tuning. Hopefully someone here can help with specific suggestions for your engine. I know that LT1 and cousin L31 both have combustion chambers designed to promote faster combustion. L31 engines generally require less timing than previous design engines to produce the same power. IIRC the LT1 engines are more forgiving of excess spark advance due to reverse flow cooling and they often tolerate a beginner's eager attempts to find best power when another engine may not. Generally, racing fuel having higher octane and a consistent blend with fewer light end HC's tends to produce more power than pump gas if spark advance is increased over stock settings. But some calibrations use a combination of advance tables designed around good fuel and aggressive knock retard which effectively reduces timing for poor fuel. The goal IMO is to observe and evaluate before jumping in to make too many changes. Luckily bracket racing rewards careful and consistent work.

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Right. The chambers are just 54-55cc and factory 10.5:1 compression. I'll experiment with it and see what it likes.