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Got on the dyno, down on power

5K views 93 replies 30 participants last post by  maverick3429 
#1 ·
Got the car on a dyno after my cam install, and the numbers are pretty low. 250hp/260ft lbs. I should be at least 275hp, and over 290tq from what I've seen.

He showed me that there was a difference in fuel trim between bank 1 and bank 2 of 17%, so it would be pointless to try to get power out of it until it's fixed. It's not throwing any codes though, which is good... but makes finding the problem a little harder.

He got the idle and the driveability locked in, though. Full throttle AFR's are 12.1, it starts right up and idles at 800, runs really smooth and feels like it pulls harder than it did before I put the cams in, but the numbers on the dyno are definitely off. When I'm driving, I don't feel a miss or knocking or any breaking up. It's not blatantly obvious to me that there's an issue.

He thinks it's a spark problem and told me to put new plugs in and front O2 sensors because maybe I fouled them up by running the car untuned for a few days. But I don't know if that would make a 30hp difference. What else could cause a bank-to-bank difference in fuel trim like that? An exhaust leak on one side before the front O2 sensor maybe? I just want to cover all the bases before I go back and try again next week.
 
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#2 ·
The more I think about it, the more I think it's an exhaust leak on one side... probably from the x-pipe to header joint. What's an easy way to check?
 
#5 ·
It's my first run, I don't have a baseline. But this shop tunes mustangs constantly, the tuner is very reputable, and he said I should be making at least 270hp at a minimum. He's gonna charge me next to nothing to run it one more time after I fix everything just to make sure.
 
#4 ·
One way to check is to have someone cover you exhaust tip with their hands while you listen for any leaks in the system.

If there's any leaks you should be able to hear it pretty easy.
 
#8 ·
HP292 cams
Bullitt intake manifold (twin plate throttle body)
BBK CAI
BBK Underdrives
UPR offroad X
Flowmaster catback

This was on a Dyno Dynamics machine
 
#29 ·
The torque is very low, a stock 2V will put out 240 to 245 lb-ft at the wheels. My base run way back when, two days after I bought the car and dead stock except for a crappy aftermarket CAI the original owner installed, hit 243 lb-ft.

The poor condition of the plugs could have a bit to do with that, however have you done a compression check?
 
#13 ·
Still running stock exhaust manifold? Long tubes would probably help out a lot with those cams.
 
#18 ·
Stock manifolds, yeah

But I think I'm gonna put some longtubes in before I go back for another run

This tune is fine for every day driving until I can get everything tuned up
 
#15 ·
Just pulled a plug out of curiosity, of course it's a Motorcraft OEM

I'm pretty sure they're the original, because it's brown and the electrode is almost gone

Damnit... all that work putting cams in and I didn't think to change them!

I feel stupid now lol
 
#31 ·
How would your tuner know if your cams arent properly installed? There is no way for him to tell. I bet both sides are probably out of spec if you didnt degree. My tuner thinks my factory cams cams are off cause my hp flatlines at 5300rpm.
 
#32 ·
Without adjustable cam sprockets "degreeing" cannot mean anymore than checking the valve timing--however it is not unusual for aftermarket cams to require (or greatly benefit from) using adjustable sprockets.

That would explain the low torque as well.

The factory cams can suffer from a multitude of timing issues, both overall and for individual lobes, because of their construction.

The lobes are made of sintered metal with splined bores and in manufacturing they are aligned properly on a steel tube that is the camshaft's "shaft". Once aligned a ball is pulled (or "pushed" hydraulically like a rifling button) through the tube to expand it and lock the lobes in place. However they can and do loosen and shift position as the years and miles go by.

There are also reports of the end cap stud, to which the sprocket is keyed and bolts up to--on Romeo cams--spinning out of position in the tube that is the camshaft "shaft", this of course throws off the timing of the entire cam.
 
#33 ·
Damn sorry to hear hopefully it is the plugs. I'd change those out, and put in some long-tubes if you can. I don't see an exhaust leak causing a loss of 20hp+, unless you had some big ass holes in each primary of the manifolds lol. If you're still not making power then I think the timing/cams are out of sync. What type of dyno? Even if it is a loaded mustang dyno, those numbers still aren't right. Honestly, you should be making within 10hp of what I'm making (301/305). I may have long-tubes but I run the stock intake, so you should be fairly close since you have an intake.
 
#34 ·
The stock manifolds are NOT robbing you of 30-40hp...just out of curiosity why is it tuned so rich at wot...12:1 is more for a boosted car...you should be closer to the 12.8-13.2 range...depending on a few factors...also the richer it is the harder it is for the plug to ignite it...especially if the plugs arent worth a damn
 
#35 ·
I agree as to the AFR being too low at 12:1, I missed that. That is the range the stock tune gets into, even high 11s, in open loop with high loads. Also, both very rich and lean mixtures are less ignitable, with the lean side being the most difficult...
 
#41 ·
I was just about to say, your tuner doesn't know the the o2s are useless at wot? .038 gap is also pretty tight. I'd run motorcraft plugs gapped alittle tighter then factory, but not .038.

I think the cam timing is off to be honest.

Can't he load the stock oem tune and look at the STFT on bank 1 and 2 and that will kind of hint if the cams are out of degree?
 
#44 ·
Hopefully dude! Get that bitch back on the dyno, if the problem still occurs, I think a cam might be way out of spec.

Good luck man, hope it all works out!
 
#51 ·
I pretty confident now that it isn't the cams, the power definitely came back after doing the plugs.

Ham,you can breath a little easier. I did a quick search on the Dyno Dynamics. Most tuners are aware they read generally 10-15% lower than a Dynojet. They also can be manipulated like a Mustang dyno to read about anything you want. Is your tuner fairly new at the game?
I read that too. The fact that he said I should make 270-280 tells me that the dyno reads lower than some others we've read about online. But he is THE go-to tuner for mustangs in this area. He definitely knows his stuff, and comes highly reccommended. They had some pretty nasty cars in there getting worked on, mostly mustangs, and a magnacharged challenger pushing 1000+hp.

12:1 at wot NA? Wayyyy too rich.
Maybe he said 12.9, I don't remember. He said it was good, that's what I remember.
 
#46 ·
Ham,you can breath a little easier. I did a quick search on the Dyno Dynamics. Most tuners are aware they read generally 10-15% lower than a Dynojet. They also can be manipulated like a Mustang dyno to read about anything you want. Is your tuner fairly new at the game?
 
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