GT-ER

Today I went again with my buddies C55 to the dyno with his new mods and it's still weak as hell.

When I went last time, his car put down 289whp with 305wtrq stock with just a Renntech airbox. It felt like a dog down low though which is weird cause it put down a nice amount of torque but it would barely spin it's tires. His A/F ratio was also in the mid 14's....yikes!

I installed a new MAF and fixed a few vacuum leaks and BOOM...now the car spins it's tires with ease off the live. I installed Kleeman headers with no cats, made a true dual exhaust and Eurocharged reprogrammed his ECU.

Took the car today to the dyno and to my surprise, the first run was 289whp. WTF!!!

The best run was 297whp with 299wtrq ( 8whp gain with 6wtrq loss ). A/F ratio was even LEANER this time...touching 15.0. This is crazy!

What could be wrong with this car? The only CEL codes it has are due to the primary cat deletes and that's it. The LTFT's are fine and the car drives fantastic. It's driving me crazy.

mkonei

How is it the worlds slowest, if you arent racing it? Dynos are meant for tuning, and unless you have back to back runs, on identical days...you could just be wasting your time. People get way too caught up in dyno numbers, especially when they can be manipulated so easily.

GT-ER

I did before and after runs of the mods...Headers, no cats, dual exhaust and EC ECU only gained 8whp and lost 10wtrq?

Plus, it's a dynojet that tends to read high and most people on these forums with the mods I have installed get over 350whp or so...yet this one has 297. That's a HUGE amount. He also was dead even when he raced a bone stock Trans Am LS1 that ran 13.8@101mph.

FrankW

Any time you loose back pressure you are going to see loss of tq.

And obviously his a/f is fubar for whatever tune he has got.

SaMaS

+1...

GT-ER

His A/F is fubar because their is something wrong with the car, not the tune. The car was lean as hell even before the tune. There is something wrong and I can't figure out what it is.

Lenin

When was the fuel filter changed? Was that OEM? Any way you can check the fuel pressure at the rail?

GT-ER

Can the fuel filter be replaced in a C55? I know it can't in me E55.

I though about checking fuel pressure...but it doesn't SEEM like it's fuel pressure since even in low rpms it's lean and it doesn't get leaner the higher it revs...it just stays the same. But it's a good thing to test.

Nachtsturm

My stock Trans Am Firehawk ran 12.97@110 and my 02 TA with a lid ran 13.5@107. 2.35 60' (Leaving at idle) My CLK55 ran 13.0@108.xx with headers and tune. Granted when I ran the CLK55 the conditions were not nearly as good but an LS1 and a M113 AMG car are actually fair game when stockish. Sounds right to me. Maybe NA cars just don't like your air.

I would check fuel pressure just to be sure though.

RLx02

That does look low. On a dynojet with k&n's, kleeman tune and headers with primary cats removed I pulled 337.8 whp/345.4lbs-ft. I ran a 13.1 with bigger 19" rims and just a LET tune when I put down around 305whp so I would guestimate that it should be around 12.8 or so now, esp if I put on my semi-slicks.

Dirty maf? I hear it can lead to sluggish performance too.

GT-ER

The maf has already been replaced with an oem one. The weird thing is that the car feels fantastic driving around slowly. It purrs like a kitten at part throttle and feels great. At WOT it pulls pretty decent ( like a 300whp car does )...but it's just not nearly as quick as I expected it to be. Especially after putting over $2K in aftermarket parts only to get 7whp more out of it. Yikes!

BryanW203

How many miles?

I have seen the flaps in the intake break and cause run ability issues, but not throw a cell, also check for intake gasket leaks.

Nachtsturm

My CLK is trapping 108-109 prior to the renntech cf airbox, the C55 in question should be the same. Dyno's don't are a tuning tool, take it to a 1320, if it is trapping close to 110, then 290whp doesn't really matter. Keep in mind its no E55.

ANother thing to keep in mid is the altitude, this directly affects D/A which will hurt an NA car more than a FI car. Not sure where in PR you are, but I know its pretty mountainous.

GT-ER

It's got almost 100K miles. I actually did think about the intake flaps...but I've searched and never found a thread on this so I assumed it's not a problem area.

It will not trap 110...I doubt it'll even trap 102-103mph. It raced a trans am that trapped 101mph and they stayed side by side.

Again, bone stock it put down almost the same power than it did with all the mods I put installed on it. Some people here gain 50-70whp with all the mods I did...and I gained 7whp? No way. I'm not even expecting 40whp...but maybe at least 25-30whp.

MBfinatic

Have you done a compression test?

GT-ER

No, I had the chance when I changed the plugs and forgot ...but do these engines tend to fail? I mean, has anyone ever had one go bad naturally aspirated?

MBfinatic

I dont know but I have not seen someone with the same problems as you.. Maybe you should just give it a try.

GT-ER

Yeah, it's on the list. The car isn't mine so I can only work on it every once in a while.

MBfinatic

Well were is the owner? He should be on here asking questions!!

GT-ER

He's not very internet friendly. He likes the car and likes to go fast, but it's not his passion like it is mine.

I have the car today so tomorrow I'll try out some new things.

Mark.D

Any idle issues?

GT-ER

Nope...smooooooth.

I'm taking the fuel pump out today to check it out.

kent426

I'd check the easy stuff first:
Spark plugs, then wires and coils. Usually higher mileage cars suffer from injector clogging too, doesn't hurt idle much but definite loss of top end power. The problem with the C55 is no inline filter, just one in the tank.

monkeyla794

Well were is the owner? He should be on here asking questions!!

GT-ER

Took the fuel pump out and it was very clean. As a matter of fact, the tank inside looked NEW all around. I put new spark plugs in a few months ago and all the wires and coils checked fine.

Eurocharged reprogrammed the ECU yesterday again with some tweaks and the car feels pretty good. It's not staining the tips so I guess it's not so lean anymore. I also ordered a brand new maf ( the previous one I put in was used ) to make sure all is good since they apparently seem to give a lot of trouble.

Stay tuned for the next dyno, hopefully I can get at least 320whp out of this dog...lol.