Dyno'd Today - POOR HP Numbers - HELP!

What color is the smoke? White? Bluish Gray? Black? When my number 8 piston got fried I had smoke coming from the firewall and PCV valve. Does you car run rough at idle or anywhere up to 4500rpm? It could be a fuel problem but that wouldn't cause the engine to smoke.

2000xp8 said:

It's actually a common mistake people make, especially one on a fox. Dyno fixes nothing. All it does is let you fine tune the fuel pressure and timing. Usually no more than that. The whole tune thing is overrated, a good performance shop can get the same results as a dyno, without the dyno. (5.0's only)

How old are your valve springs, and what lift are they rated for?

I also wouldn't mess with anything else until you get the 42's, i didn't see what size you had, but i'll assume 30's or less, which is not nearly enough.

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you might wanna ck that statement, i can ck timing and fuel pressure in my garage-maybe not the timing curve, but most dyno places i've seen/heard about will recommend that you use no more than 42 psi anyway for baseline pulls seeing as that's what most injectors are flow rated at. Dyno runs will not always fix what you have wrong, but treachery had some small issues that were most certainly related to tuning-hence the trip to the dyno, and the belief that some things could be fixed.

the whole tune thing is overrated? hmmm, ok, tell ya what, go take your car to get a dyno tune, if you've got a fairly decent package of bolt ons, there's a good chance that you could find 20 or more "hidden" hp...that doesn't sound like smoke and mirrors to me-tuning is so that each individual car runs at its full potential...the fuel and spark tables preprogrammed into the computer don't necessarily fit the needs of every engine...the way your engine is setup is different than mine...so, timing curves and fuel tables need to be adjusted to more closely match the requirements of the engine. still sound like bs to you? you'll be alone...most people i've talked to in here share the opinion that a tune is a necessity if you're running a blown engine, where fuel and spark are MUCH more critical that N/A setups. you could just crank up the pressure and hope it works, and alot of times it does (hence the whole FMU thing)...but not always, even if it keeps the top end fed under acceleration, then your low end is being fed too much fuel since injectors are designed specifically to run at a given pressure, higher pressures mess around a little bit with the flow rates, and fuel delivery.

valve springs are a decent concern, but unless he's running into nasty float, or coil bind, he should be ok for right now...

i agree to a certain extent about the injectors, but the FMU was designed with purpose in mind...not the best fix for fuel delivery i agree, but if it were that bad an idea, they would've abandoned them long ago...

perhaps you need to do a little more research first, instead of stabbing in the dark and making pompus accusations and assertions of how to make the most from everyone elses toys...their cars are not your car, different combos have different requirements...

perhaps he's got some gremlins, but to tell a person with a supercharger that a tune would do them no good at all is just a load of

I saw a problem similar to what your seeing on the dyno. Turns out there was too much oil in the pan. Just an Idea.

how are the spark plug wires? My buddy and I were at the dyno with his car, and his wires were causing spark loss. Engine would fall on it's face right around 4500 rpm as well. We changed the wires on the dyno, and BAM!!!!no more cutting out, and the car gained about 70hp(no BS) Check your wires out as well

Treachery,

Too much fuel can cause the fire to go out, what AFRs are you running where the problem occurs?

Also, at higher fuel pressures the fuel pump doesn't flow as much as it's rated for.

I'm running Denso Iridium plugs with 8 psi without issues.

Good Luck, Don

If you have 52lbs of fp at idle that could be a problem. You should have around 40. Your FMU doesn't start working until you see boost. Do you know how an FMU works. If you have a 6:1 setting on the FMU then you may be seeing 100psi of fp under boost. Is it possible the smoke is unburneed fuel? I hope I re

If you have 52lbs of fp at idle that could be a problem. You should have around 40. Your FMU doesn't start working until you see boost. Do you know how an FMU works? If you have the fmu @ 6:1 you may be seeing 100psi of fp under full boost. You may be flooding the engine or maxing out the injectors. Is it possible the smoke is unburneed fuel? I hope I read enough. The 52lb's of fp and and fmu strikes me as odd.

QDRHRSE said:

If you have 52lbs of fp at idle that could be a problem. You should have around 40. Your FMU doesn't start working until you see boost. Do you know how an FMU works? If you have the fmu @ 6:1 you may be seeing 100psi of fp under full boost. You may be flooding the engine or maxing out the injectors. Is it possible the smoke is unburneed fuel? I hope I read enough. The 52lb's of fp and and fmu strikes me as odd.

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i already talked to him about that one with the same concern, he told me that when he was doing the pull, the FP was pushing like 70 under full load...but, like gt90 mentioned before, the pump won't put out full volume at that pressure.

he did mention picking up a set of injectors i believe-can't remember though, i cleaned out my inbox...doh!

I think you need to get a tweecer. We did a kenne bell install on my buddies 94 in the garage and never brought it to the dyno. Like some one else was saying there is only so much you can do with dyno tuning...its really not all its cracked up to be. Get a tweecer and learn exactly what your computer is doing and why...then tune the car yourself to make it run the way it should. we make amazing progress tuning my friends car in the first three hours. also get some bigger injectors...def 42's and drop that FP down a little bit...i think you are floodin it out too

don't you have to leave the unit plugged in constantly? i've been tossing the idea around of acquiring one, but i still have alot to learn about FI...

well its actually just a piggy back setup...you leave the module on top of the ECU then just run a USB cable into the glove box to plug into the lap top. We were doing some testing for the newest software package for tweecer and it is honestly one of the easiest systems to use. It has quite a steep learning curve and there is not a ton of published info out there but once you understand the most important scalars and fuctions...its quite easy to tune the car. My friend actually just removed the blower and could still tune the car with a 90 mm MAF and 42# injectors on a stock N/A motor. We also installed a wide band in the h pipe and you can read out the AFR in real time within the tweecer program and also watch 14 other sensor functions at the same time....amazing software.

Whats your fuel pressure doing when it cuts out? Does it stay pretty smooth or drop down? Have you tried pulling the codes? Hows your spark plug wires also?

Did we ever get an answer as to whether this is a MAF car or SD?

These symptoms have been all too common lately. I'd say that I've seen this same 4500 rpm ghost rev limiter problem once every other week for the past couple of months. The problem lies in either the fuel, spark, or vac.

I know that doesn't narrow it down enough for ya but I'd bet a dollar that it's not the wear of your engine or anything near that ominous that's cuasing the problem.

Try changing the distributor again. I had the exact same problem with an MSD dist. I know you tried a stock one, and had the same problem, but I would try a third.

Problems tend to be simple, not complicated. And just because you changed a part once doesn't mean that part isn't faulty. Good luck.

After the wires, you might think of replacing the TFI and/or the pickup coil in the distributor if the replacement distributor was not new.

Have you checked the coil itself? What about the wiring? If you aren't getting enough voltage to the coil, you wont have a strong enough spark and it will get blown out at higher RPM's. With all the changes you've made, you might have broke a wire inside the insulation.

i'm not a pro here but i had the same problem on my vette and i was getting knock retard at the same rpm. it felt like the car just fell right on it's face.

jrichker said:

What is your fuel pressure? Did the dyno provide a wide band air/fuel ratio gauge? If so, what were the air/fuel ratio readings?

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Agreed. What kind of fuel pump and regulator are you running...hopefully not stock.