bgbfflochp

Alright, I'm trying to get ready for my car to get tuned with an AEM EMS unit later this month. I went ahead and installed my 550cc injectors and I'm about to put a 3.5" pulley on the Comptech SC. Keep in mind, the problems I list below were happening even before I put the new injectors in.

I'm having problems with my fuel somehow. First of all, I've had to change spark plugs 3 times in the last 9 months. The car will start, and just gurgle for 5 minutes (A/F reading 9.6-9.8) and idling at about one bar of rpms...it doesn't even make it up to 1000 until the A/F finally goes up to normal. It does this after the car is turned off for 9 or more hours. I guess I'm not too worried about this if it's going to be fixed when I get it tuned with the AEM EMS. Also, when I get on it, the car's rpms won't go past 8000. The wideband reads 12.5 until about 6500 rpms, then it goes to 10.0...and then at 8000 it goes to 9.6 and cuts all power. It sounds like it's spitting stuff out of the exhaust and the rpms won't climb any higher than 8500. It's tuned (horribly I might add) with a V-AFC right now. I finally got adventurous (i don't tune my car...don't know enough about it) and started taking fuel out. Nothing changed, so I took all the fuel out completely. It still reads 9.6 and cuts at 8000 rpms. Is this just a faulty V-AFC...v-afc install, or tuning? Or is there another problem I might need to worry about before I drive two states away to get my car tuned by somebody that knows what they're doing. I didn't have any of these problems until I put the 4.25" pulley in, and I took it to my nearest dyno to get tuned. I've had the problems ever since. And then when I'm driving at a steady speed (48mph in 4th gear), the A/F will just randomly jump to 17.0 or even higher for no apparent reason.

If you guys think it's bad tuning, I won't worry about it, but I'd hate to drive 2 states away and fly somebody out from Oregon to find out that he can't even tune my car because of another problem.

So I guess my question is, do you guys think it's the fuel...or something else?

Also, what is the normal rpm for idle?

Thanks,
Dave

Right now, I have:
Comptech SC...4.25" pulley
front mount intercooler
V-AFC
comptech 4-1 headers
comptech testpipe
single exhaust
techedge wideband
550 cc injectors

Slows2k

I'm going to step out on a limb here, and say the VAFC is not able to compensate for the 550's. I'd swap the originals back in untill the EMS is tuned.

Stay out of boost with the little pulley as well.

AusS2000

This point has been beaten to death, and there are some accounts to the contrary, but using a VAFC with an upgraded SC is just asking for trouble. I mean, you spent more on the gauge to check your A/F than you did to actually tune it.

I expect the problem in your case is that you have big injectors and so heaps of fuel is going in. Then, you're trying to pull some fuel down low with the V-AFC, but it's not wideband enough to pull enough fuel, and in the mean time it's probably advancing the ignition drastically.

This is not a good set up.

bgbfflochp

but once again, i was having this problem before I put the new injectors in. I just put the new injectors in today to get ready for the AEM EMS install/tune and smaller pulley install. I don't plan on driving the car until the 26th when I take it to Alabama to get Sean from Torque Freaks to install the AEM EMS and tune it correctly. I just wanted to make sure you guys think it's the V-AFC not being able to adequately tune the car and not something else. I don't want to waste his/my time and money.

Thanks for the replies,
Dave

Slows2k

Have you been messing around with the static Fuel pressure? I'd put a gauge on it and verify it. The stock Comptech Kit should not have these driveabilty issues. The 550's will make you driveabilty worse. Is the 4.25 pulley the stock Comptech pulley?

fperra

You could have a bad injector. Send them to RC Emgineering for flow check and tune. Also, what injectors are they? I've seen some problems with replacement injectors where the spray tip wasn't long enough for the intake manifold socket. The spray pattern wasn't making it to the air flow unimpeded .

Slows2k

A failed injector is possible, especially when using much higher fuel pressures than normal, which is what you have with an FMU. If the injector was that bad, I would suspect misfires at any speed as well as miss-fire DTC's

bgbfflochp

ok, not exactly sure what static fuel pressure is...we've upped the fpr and taken out (or at least thought we're taking out) with the V-AFC.

The stock pulley for the SC is a 4.5"...so i went to a 4.25".

I had this same problem with the stock injectors that worked fine with the stock SC for 9000 miles. We added the new pulley (4.25") and front mount intercooler, and when he tried to tune for that...I started having these problems. I've just installed new fuel injectors (RC Engineering 550cc) today (after about 2-3 months of having this problem)...and it's still having the same problems. The guy tuning the car really seemed to have no idea what he's doing...unfortunately, neither do I. He kept insisting on adding fuel with the V-AFC and an hour later, he finally listened to me and realized you can't add fuel with the V-AFC. So then he went to town on the FPR and took out fuel with the V-AFC from there. There are no positive numbers in the V-AFC now. With that small of an upgrade to the pulley, and the addition of a rather large intercooler, I would think the boost would be about the same as the stock SC pulley and no intercooler. I know he added a lot of fuel from the FPR. I would think he added too much...I don't see why he would have to add too much fuel with the new setup. He made the comment "I've added about as much fuel as I can add with the FPR" at one point. I started taking some out today, but I'm scared to turn it too much because I don't really know what I'm doing. I'm really not worried about my car being tuned for power. I'm trying to get it to crank and idle normally no matter how long the car sits, and hopefully quit having to change the spark plugs so often. I don't care about the power right now because sean is going to install an AEM EMS and tune it for me later this month. I'm just worried that something other than too much fuel might be causing these problems, and I don't want to fly him out here and waste his time.

I really don't think it's the injectors, because I have the same problems with the stock and now the new injectors. But then again, I don't know much about installing/tuning anything. I figured the guy that's tuned thousands of cars (no S2000's other than a stock one) would have a much better idea on tuning it than me. I'm hoping he just added too much fuel. Later this month, I'm meeting Sean in Alabama, where I plan to install the 3.5" pulley before he takes the keys for tuning. I don't see how the A/F can stay the same, before and after I take all the fuel out with the V-AFC. Would it be pointless to take the V-AFC out and see if I have the same problems? To me, it doesn't seem like the V-AFC is doing anything at all. I've made such dramatic changes to the fuel delivery and not getting any changes in A/F.

Slows2k

I would remove the VAFC, or change all the settings to 0's. You need to get the car running normally at rev ranges you can at least drive the car at. Get the FPR reset, I believe the Spec is 55psi, I'm not sure as I don't have a comptech. You will need a gauge to do it though. I would also go back to the stock injectors. The stock comptech kit should run fine below boost with the larger pulley installed. I would not trust any fueling increases in boost.

It will take your next tuner more time if he has to undo your previous ones work.

modifry

I have a stock Comptech SC and my pulley is 5". So 4.25 is a significant change.

On the other hand I just had a friend of mine install a Comptech on his '04 and he used a 4" pulley (post here ). We guess-timated boost to be 7psi and the stock injectors were good enough for 310 RWHP, with room to spare, since even with my A/F hack they never went over about 82% duty cycle. The only changes made were the 4" pully and the A/F hack, everything else is out-of-the-box and un-tweaked.

Unless you're shooting for significantly more HP I would at least attempt to run on the stock injectors.

I have to agree with some of the others here, get the car back to where it runs before trying to tune it, then make changes one step at a time. Installing bigger injectors on a car that already runs poorly does not sound like a good approach.

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