GM EFI system on a Air Cooled beetle

[ggenovez]

Hi all.


My son wants to turbo a air cooled vw. I was thinking of using a gm tbi system for fuel management. My biggest concern is the distributor

Any way to retrofit it?


Thanks
Any other pitfalls I should be concerned with? What about the CTS?

[dave w]

Incorporating a MSD 6a into the VW ignition system to trigger the TBI computer will allow using the original VW distributor, see attached pic.

dave w

[ggenovez]

Will that still allow the ECM to retard the timing if there is detonation?

[RobertISaar]

if you impliment a knock sensor(and filter), yes.

finding one that matches the characteristics of the VW engine may be difficult though.

[ggenovez]

Thanks Robert.

WOuld I not be able to use a GM one? I figured a knock sensor is a knock sensor...

[delcowizzid]

heres a conversion thread from our forum http://pcmhacking.net/forums/viewtopic.php?f=15&t=3498 uses an australian model nissan pulser dizzy with a little shaved off the diameter so it fits in the hole and thats it fitted in there

[ony]

ON 1968-70 STATIONwagon models with electronic fuel injection the dist has an extra set of points in the bottom to trigger the fuel injectors might be able to use them for something.

[RobertISaar]

Thanks Robert.

WOuld I not be able to use a GM one? I figured a knock sensor is a knock sensor...

not quite.....a narrowband knock sensor has about a 1KHz bandwidth where it reliably picks up on the frequency that a given engine will generate knock at(which is determined by bore size). i can't think of many/any GM engines off-hand that have a similar bore size to the VW(which one is it, BTW?), maybe the 1.8/2.0 four-cylinder engines of the late 80s might match up well enough?

the reason i'm mentioning GM is that you'll need to match sensor impedance as well, generally with GM there are two setups there, a ~4K one and a ~100K one. there is also the oddball dual knock sensor stuff that i believe are 8K, but they're so far out of the range of what you'll need that it won't be relevant.

4K vs 100K comes down to which ECM you plan on using. most, if not all of the C3 ECMs use an external knock filtering module with a 100K sensor. the P4/P6/P66 models tend to use an internal filter with a 4K sensor, but some can be modified to use a 100K/external filtering module.

[billygraves]

Hi all.


My son wants to turbo a air cooled vw. I was thinking of using a gm tbi system for fuel management. My biggest concern is the distributor

Any way to retrofit it?


Thanks
Any other pitfalls I should be concerned with? What about the CTS?

In my opinion, I would be very concerned with a TBI set up on a Turbo. As any turbo with TBI, I would never. Fuel distribution is critical. The GM TBI had some distribution problems and were set on the rich side. Some fuel steering with the Blades at part throttle. Some was due to the intake. I would elect a Port Fuel. (TBI was much less money for OEMs)
As for a Knock sensor? I do not think you will be able to get it right, ever (without a lab). The characteristics of a alum opposed 4 cyl air cooled are a "little" different than a water cooled V-6 or V-8. (Most small blocks had WET knock sensors.) If you only knew what went into a knock sensor selection you would drop the idea. (I tried to put a 7.4L knock sensor on my 454 race car engine. After I discussed it with the right engineer, I dropped it.)\
I think a Turbo PFI VW would be the Coolest!!! Similar to those Ok Street Racers! If you get it right, you'll need a set of wheelie bars!

[EagleMark]

Here you go!

http://www.gearhead-efi.com/Fuel-Inj...BI-Conversions!

[ggenovez]

Thanks guys. I really appreciate it.

Billy brought up an interesting point about the TBI and my assumptions.

Rather than assume I know anything, why don't I ask the question in a different way.

If you had an air cooled VW, and wanted to turbocharge it and use EFI (with knock) what would the group recommend?

I know that megasquirt is available, but I think its too expensive VS a 7730 GM ECM. That being said, I am open to discussions. I don't want spend $300 to save $.05 right?

I know that air cooled Porsche's did use a knock sensor. The whole idea of using EFI was to protect the engine from detonation.

All that being said, if this was your project how would you do this?

Thanks again, I appreciate everyone's feedback...

[dave w]

A few years ago, I helped a co-worker with a supercharged air cooled VW. We initially used the '7730 with limited success. The Megasquirt system seemed more capable of dealing with the "One Off" nature of a supercharged air cooled VW. Shortly after we got the engine running with Megasquirt, my co-worker relocated to the east coast. I don't have any information on the progress of the project since he moved.

If I were to build a turbocharged air cooled VW engine today, I would use a Megasquirt system.

dave w

[ony]

them old 1968-1971 station wagons was port injected efi, they where pretty neat thay had a adjustable pressure regulater on them set the fuel pressure to around 29 pounds and get 35-39 mpg at 55mph. I don't know if a turbo would work on that type set up. I seen super chargers on the old bugs in magazines a long time ago. what cc engine do you have? I had a 4barrel afb on a 1800 cc with a 110 ingel cam it would fly.

[Scorp1us]

Your mods would be pretty standard I think. You would only need a 2bar MAP and do a standard dist conversion (points to electronic pickup)
Maybe use a setup off a pontiac firebird?

[delcowizzid]

you dont need knock sensing to be safe its just there so if you fill up with crap gas it has some sort of way to limit low octane detonation and to keep you out of trouble with pump or sensor failures i run so many cars with no knock sensors its not funny if hey dont have them stock i dont add them LOL.running cars into the tens with no knock control N/A and turbo converted.ide be following the thread i posted above and using 1227165 ecu and the 2 and 3 bar code we use for them down in newzealand/aussie its made for the job and the xdf is pretty much the most fully defined youll find.