2G What is the limit for the stock fuel system?

[Thecarfixerguy]

I’m making a push to get my car on the road this season. I have all the mechanical in good shape, I built up the engine and have a decent turbo(FP6951S) and a CX racing intercooler. This winter I want to go through fuel and engine management, but in the meantime it’s all stock. Stock injectors, fuel pump, ecu, etc… I’m probably just going to put on a manual boost controller until I finish the next phase. I’m just wondering what my limits are until I can get this thing really tuned up. All suggestions are welcome.

 

[curt-s]

You're going to find it difficult to run the 6851S (68HTA v3) on the stock injectors, pump, and ecu, in anything but low/medium boost.
At the level you need to run it at until you get ECU and fuel tuning capability, you would have found a 14B to be more responsive and fun.

 

[Thecarfixerguy]

What do you consider low/medium boost? 10 Lbs? 15 Lbs? I know I won’t be able to use the turbo’s full potential until I get the fuel system done, and I originally hoped to have it all done at once. However, my available time to work on it and budget goals are telling me that won’t happen this summer. So I’m just trying to get it on the road for now. I bought the car disassembled and it had been sitting for years. I’d like to figure out what other surprises it has for me once it’s on the road so I can sort them out this coming winter.

 

[chrysler kid]

The stock ecu sees the turbo sucking in more air and will cut the fuel because the stock ecu still uses the stock air/fuel map and sees the extra air flow as a problem.

The factory ecu isnt smart enough to calibrate a new safe air fuel mixture

So the most the car would probably let you spool is probably 12psi, and at that level the boost would feel pretty lethargic. The extra air charge pressure needed to go through the intercooler will make the car feel slower than the factory setup

So how do you solve that problem
You need a new ecu or tuning software to change the fueling tables for the extra boost, and then larger fuel system to add to make more boost.

The next issue you will have is tuning a 25 year old vehicle means they will need to do a health check on the system. You will need to boost leak test to find that the throttle body shaft seals are blown, and the biss screw has a leak at the o-ring

If you want to play credit card speed games, you can expect a reputable tuner to charge you another $400-$600 in diagnostics before a tuning session.

So here's the real question, how dedicated are you to the platform. You can spend as much money as you want to reach a certain horsepower, but 3 weeks later have the clutch slave cylinder go out, are you the guy who tows it to a shop to have that $60 part replaced for $600 and two weeks down, or are you the guy who goes out and replaces it himself

If this is THE car, the platform, you will need to realize it takes more money to stay on the road then any other platform on the market. If you are the guy who turns wrenches on the weekend for fun then this platform is just as simple as any other 25 year old vehicle

Just know that there is no finishing point with these cars, you can spend every dollar you have at a shop and the car will still have an issue the next week where it requires another thousand dollar repair to keep it on the road.

To be blunt, if you have to ask these questions, "what do I need to do to run this, or make this horsepower", I can tell that youre already not dedicated enough to do the research for a "fun" project, which means you are in over your head when it comes to doing a simple boost leak test

 

[Thecarfixerguy]

So here's the real question, how dedicated are you to the platform.

I don’t think I’ll be paying a shop to do any of this since I already have a 4,000 sq ft. auto repair shop, ASE certifications, 4 hoists, and 3 full time employees.

My experience is in stock passenger car repair though. This is the platform I want and plan on keeping this car for the long haul always improving it. I had one in college and always regretted selling it. At that age I had no money or experience to do anything fun with the car. That has changed. I know how much it costs to do things like this. I’m probably $5G in parts to get where I am now if I add it all up. I’m just trying to take it in phases. I still have suspension/brakes/paint/etc… to work on when I get done with fuel and tuning.

This is a project for the long haul. I plan to have this car in tip top shape in a few years. As soon as I have it on the road I will be working on putting together a build list for engine management, but I still have some homework to do in that department as my field of experience has always been repairing vehicles with stock configuration.

 

[chrysler kid]

I don’t think I’ll be paying a shop to do any of this since I already have a 4,000 sq ft. auto repair shop, ASE certifications, 4 hoists, and 3 full time employees.

Great to hear, these cars aren't that complicated, they just require dedication and attention to detail.

Boost leak testing is the most important piece in ensuring proper airflow into combustion

 

[curt-s]

Nice to hear about the dedication and the experience/knowledge to back it!

But, yes, about 12psi or so on a 6851S for the stock fuel system and ECU. The good thing here is you've already got a 2G MAF and the 2G timing table, so you can go a bit further than a 1G, but you're still very limited. Without a method of monitoring or logging knock, you're also running a huge risk pushing anything above that if you were to lean out.

It's going to be very lethargic and slow at 12. Slower than a 14B due to the increase in lag.
BUT you'll be driving something you built, so don't incite or respond to a race request and just enjoy the car.
In fact, it will give you some time to see if there's any other gremlins lurking about in driveline, suspension, etc. Personally, I'd like to find those out at 12 instead of 25

 

[Thecarfixerguy]

Just an update (like anyone has been losing sleep wondering what I decided to do). I was hoping I could at least get the car running and driving close to stock with the stock ECU, but since it looks like this thing will just be a turd until I get fuel management under control I have DSMLink on the way. Now I’m working on acquiring injectors, wideband, fuel pump, etc… I can’t wait to rip in this thing.

 

[steve]

While your waiting, like I suggest to everyone, read the original 1990 Technical Information Manual and the follow up with the 2G release. There is so much information in each.

https://www.dsmtuners.com/attachments/technical-information-manual-talon-laser-1990-pdf.548037/

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Then pick up the various manuals for your year car.

https://www.dsmtuners.com/forum/articles-manuals-documents.262