Today I brought my 88 TII in to a local shop to install a SAFC-II and do a few pulls on the dyno to smooth out my fuel curve. Since I've purchased the car, I've installed the normal bolt on's: intake, downpipe, cat delete, HKS exhaust and BOV, koyo rad, ported the wastegate and turbo inlet runner, and emissions removal. With all that, it's ran well, but not great. AFR's kinda all over, usually on the lean side, so that's why I picked up the SAFC, just to find a consistant safe AFR. I know it's not the best choice for tuning, but I got it from a friend and I just want to be safe till I rebuild my engine.

Prior to the tune, my AFR's (AEM Wideband) usually were in the mid-high 13's and 12's in boost on a good day. I'm a conservative driver usually, but I know those numbers aren't safe. The shop I went to is generally a DSM shop, but their tuner has dealt with rotaries before, though he hates tuning them. Anyway, he did a few pulls and came to me with an issue. Up to 4,500 RPM, it was responding well to the SAFC and was in the 11's for AFR's, but once it boosted above 4,500 rpm, it leaned out to the 13's. He didn't want to push it any further as he wanted the numbers in the 11-12 range. He said that he had the fuel corrected up to 50%, but once boost hit it stopped responding to the corrections. It's still running fine and the SAFC helped as my AFR's are in the 11's instead of 13's while driving. I don't have the dyno graph yet, but he said it did 200whp.

They discovered 3 fried wires going into the main harness that are related to the previous owner somehow. I forgot about them honestly as I noticed them in the past, but everything works and nothing has ever been funky. But in their limited rotary knowledge, they suggested that it could either be the secondary injectors not coming on, as they would normally come in around boost kick in. And the fried wires may have something to do with that. Or the fuel pump isn't pushing enough fuel to cope with the higher power demands. I should mention that I've never done anything to the fuel pump, but I did have the stock injectors cleaned professionally and they flow perfect.

I've had my car for 4 years, could it boost to redline or generally drive at all only on the primary injectors? I don't know, but I would think that without secondaries it would blow up or hesitate or something. It's pulls strong and smooth, no 3800 hesitation. Could my fuel pump be the culprit? Should I get a Walbro and rewire it? I'm color blind, but the guy said the main fried wire appeared to be green. Sorry for the book, but any ideas?

 

What do you have for fuel mods? I don't see anything about larger injectors or how much boost your seeing at 4500 rpm.

 

It could be a number of things but that's the classic symptom of a fuel pressure drop due to dilapidated fuel pump wiring.

 

I haven't done any fuel modifications other than cleaning the injectors. I'm aware of what's required for major power additions. But at this point I'm waiting for an engine rebuild before I go for a bigger turbo, injectors, stand alone etc. I just want this engine to last a while longer til I get the funds for a full blown build. As I told the tuner today, all I was looking for was a basic adjustment to the curve as it doesn't ever see boost above 10. Conservative and safe. I'm not an expert yet, but I feel my current setup can handle the tune I'm looking for. Except for possibly the fuel pump situation. If I need to rewire that and upgrade the pump, then that's what I'll do. Then back to the dyno.

 

How about stock fuel cut or just leaning out with stock injectors?

 

i doubt its a fuel system issue as the car ran in boost up to the dyno unless you always shut it down shortly after 4k RPMs and never really pushed it.

to me it sounds like the RPM signal for the SAFC is not set up properly which is causing the mapping to cut off after half of the RPM range. did this "tuner" check to see if the RPM signal in the SAFC matched the tachometer?

 

I have a FCD so fuel cut isn't an issue. It'll boost to redline no problem. I watched him do the pulls and he did at least 2 full pulls and when I saw the graph it was running good AFR's until about 4,500, and then as the RPM's went up, the AFR's leaned out to 13's. Honestly when I drove it home it didn't seem to lean out bad when I revved it up. But I don't spend extended amounts of time above 4,500 rpm.

I don't know a ton about dyno's, but he had it all wired up etc. When I drove home I was keeping an eye on the SAFC screen and the RPM's matched my tach. I recently adjusted my TPS so I have a consistant 750ish idle and watching the screen it jumped between 740-760 every time it idled. This shop does some pretty crazy cars. If you read Modified at all, they had a mention of their 800+ hp 4G64 FD a couple years back. After talking to their tuning guy, I felt pretty comfortable with his knowledge.

 

check the voltage at the pump or the fuel pressure while driving to see if it is dropping off after 4500.

 

+1
stock fuel pump wiring is marginal at best. I saw a full 3 v increase In boost and I retained the variable voltage system.

That didn't however cute my leading issue but mine happens @ 3500 and I WISH it was in the 13.x afr range lol

 

Well, time to do some searching and get a friend over who can properly see colors to help me out. But I'll start with the wiring and see where it goes. The tune I have now is probably fine for how I drive the car in it's current state, but I'd like to get a proper tune if possible. Would there be any point to getting a better fuel pump at this point? Would say, a Walbro 255 be pushing too much pressure for the stock FPR to handle? I've always planned on getting one, but didn't as I haven't had a need or a reason to get one yet. When I get to the full engine build point of my car, I'll take care of the whole fuel system with the proper upgrades, etc.

 

A 255 is overkill on a stock turbo and fpr. It raises pressure across the board and makes the car run rich all the time. Not to mention it still needs proper voltage to work correctly. So if the pressure is falling off after 4500rpm it would still do so w/ a larger pump (albeit afr's might be ok since it flows more ...)

Measure voltage and Find out if is the pump our the voltage, them fix the actual problem.

 

You could probably just rewire the stock pump and it will be fine. Or get an FD pump for basically nothing. Either way you need to rewire the pump.