Low dyno numbers : (

[orlo]

So I recently had my car on the dyno with the mods in my sig and it put down some disappointing numbers. Even with a Posi Race port, it made just 482/446.....max boost was only 12.5 - 12.8 psi if I can remember correctly.

I'll be putting on a 4# lower next month, but in the meantime, I've been dwelling on these numbers a lot.

Obviously that boost is way too low for a ported cobra and I'd bet my longtube headers and o/r midpipe don't help. I'm thinking that the car wasn't taking advantage of the ported blower at that psi. Shouldn't it be more like 16-17.5 psi? Also , it was a 2 hour trip to the dyno and 85 degree weather, so perhaps that played a factor. I also noticed that my rear diff is leaking some oil...not sure if that would have any effect.

Anyway, I'm really hoping that adding the 4# lower will get the car making the numbers it should. Anyone care to share their opinion or have any idea the gains I could expect from the lower pulley?

 

[mofobucs is a thief]

12.8 was peak boost? #'s seem about right for what you have done.. throw a lower on and you will be happy

and the rear diff leaks in all the 03-04 's.. gotta reseal it

 

[BLUESNK]

wow that does seem kind of low
my car put down 478 HP and 503 trq on just a 2.76 upper only pulley non-ported
and of course exhaust, intake and tune
pretty sure that lower pulley is going to help a lot

 

[Monster Mach]

So I recently had my car on the dyno with the mods in my sig and it put down some disappointing numbers. Even with a Posi Race port, it made just 482/446.....max boost was only 12.5 - 12.8 psi if I can remember correctly.

I'll be putting on a 4# lower next month, but in the meantime, I've been dwelling on these numbers a lot.

Obviously that boost is way too low for a ported cobra and I'd bet my longtube headers and o/r midpipe don't help. I'm thinking that the car wasn't taking advantage of the ported blower at that psi. Shouldn't it be more like 16-17.5 psi? Also , it was a 2 hour trip to the dyno and 85 degree weather, so perhaps that played a factor. I also noticed that my rear diff is leaking some oil...not sure if that would have any effect.

Anyway, I'm really hoping that adding the 4# lower will get the car making the numbers it should. Anyone care to share their opinion or have any idea the gains I could expect from the lower pulley?

The trip is what ****ed you.. heat sink suckssssssssss... psi was low any belt slip? Thatll affect everything to.. check for any dust.. but the heat and the trip cut your numbers the most.. let it cool down and get that lower and youll see the numbers you want

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[SilverCobra7]

I recently had mine dynoed too... Drove 3hrs to tuner in 95* weather. Did let it cool down a bit but still was pretty warm. I was surprised that mine only made 13lbs of boost... When it was showing 13.5-14lbs before! Maybe it was the hot weather, but I was happy with my numbers... Especially the tune! Looking to go to a 2lbs lower later or the Stiegemeier 2.49 pulley.

 

[orlo]

Yea, the trip definitely didn't help. There's also a lot of dust on all of the pulleys, so maybe it's slipping? I'm going with a new belt anyway for this setup, but I really think the low psi is the main culprit. So with the 4# lower, I should see around 3-4 more psi, which should give some pretty nice gains. But will it be enough to bring that torque over 500?

 

[SilverCobra7]

Yea, the trip definitely didn't help. There's also a lot of dust on all of the pulleys, so maybe it's slipping? I'm going with a new belt anyway for this setup, but I really think the low psi is the main culprit. So with the 4# lower, I should see around 3-4 more psi, which should give some pretty nice gains. But will it be enough to bring that torque over 500?

The lower will definitely will up the torque! HP will depend on the timing.

 

[Monster Mach]

Yea, the trip definitely didn't help. There's also a lot of dust on all of the pulleys, so maybe it's slipping? I'm going with a new belt anyway for this setup, but I really think the low psi is the main culprit. So with the 4# lower, I should see around 3-4 more psi, which should give some pretty nice gains. But will it be enough to bring that torque over 500?

The dust on the pulleys being fixed could get you over 500 lol

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[05satinGT]

Every car is different. Even though you have a port doesn't mean you automatically break the 500 wheel mark. I took a 3 hour ride to get tuned and as long as the car was properly cooled down it shouldnt matter although it might definitely be heat soaked. Temp shouldn't matter when the numbers are corrected. Where they corrected numbers?

 

[03 TOPLESSSVT]

I would do a compression check on it also to see if you have a cyl down.

 

[Ray Lucca]

Who tuned the car??? It was Tuned with all of the up-grades, right?? How old are the plugs, gap, and fuel filter??? Changed recently?? A lot of these cars are blowing IC Pumps and relays... Ck yours, see if it's percolating. Had a KB car on the Dyno, IC relay was fried, jumped it on the Dyno, waited 3 minutes, and the HP went up by 60 HP. BAP wired, and operating properly?? Also ck. your Battery , Alternator, put a meter on it. Good luck..

 

[orlo]

The car just recently had a compression test and everything was fine. I also checked the IC pump and it's working fine as well. Plugs are NGK and were checked recently as well.

I think it all comes down to the boost. 12.5psi is really low for a ported cobra. After a better fitting belt (my current pulleys are covered in dust) and the 4# lower, I think I'll see the boost and the numbers I'm looking for. Again, the car has headers and an o/r H pipe, which drop boost by a few psi.

 

[Qwk GT]

Who tuned it? I'd assume even with heatsoak it should've pulled more. (tq wise at least)

I thought common upper ported guys were running around 13-14 psi? (Common 2.8/2.76's) Edit: Noticed you had lt's, maybe thats why.

I know I wasn't ported, but my 2.8 pulled 15.6 psi, then dropped back down to I think 14.

 

[Bdubbs]

Who tuned it? I'd assume even with heatsoak it should've pulled more. (tq wise at least)

I thought common upper ported guys were running around 13-14 psi? (Common 2.8/2.76's) Edit: Noticed you had lt's, maybe thats why.

I know I wasn't ported, but my 2.8 pulled 15.6 psi, then dropped back down to I think 14.

15.6 psi on a unported eaton isn't a common thing. The norm is around 12.5-14psi. Highest I've seen mine go is 13.5 on a cooler night.

Op Your tq seems quite low, did your tuner tell you what he set the timing and a/f ration at? What pulley setup are you running and what size belt?

 

[03 TOPLESSSVT]

You will Loose 1.5-2 lbs with those BBK's at the most. Your belt should be so tight that you have to remove your aux idler to put the belt on. Also tighten up the boost bypass valve if not already mentioned.

 

[orlo]

I just checked the belt sizing diagram and the belt that the car was tuned on is 1'' too large. That would explain the copious amounts of dust on the idlers. There is also a squeaking sound when the car is turned on that goes away after a few minutes...again, belt?? I already have a new belt on the way that should fit much better and I'll be sure to let everyone know the new numbers.

 

[OH3BLKSVT]

.yea, a loose belt will give you low numbers. change that belt and put her back on!

 

[Posi]

Every car is different. Even though you have a port doesn't mean you automatically break the 500 wheel mark. I took a 3 hour ride to get tuned and as long as the car was properly cooled down it shouldnt matter although it might definitely be heat soaked. Temp shouldn't matter when the numbers are corrected. Where they corrected numbers?

Yes corrected numbers mean other things shouldn't matter but someone with a stock size intercoole resevoir and a misplaced fan can still have to hot of i/c fluid even at the end of a dyno pull. That's why I always say if there's any doubt any of our cars will pull timing then the dyno pull should be put off for another 10-15 minutes.

I just checked the belt sizing diagram and the belt that the car was tuned on is 1'' too large. That would explain the copious amounts of dust on the idlers. There is also a squeaking sound when the car is turned on that goes away after a few minutes...again, belt?? I already have a new belt on the way that should fit much better and I'll be sure to let everyone know the new numbers.

Now that has to be a loose belt and is also why I don't go off of belt charts and also don't tell people what size belts to put on. I will if I'm running that exact combo but other than that I just tell people to buy a few different lengths to try. Then if those are still to loose then go and buy another one smaller. A 1/4" could be the difference between a slipping belt and one that doesn't slip at all.

 

[MalcolmV8]

Obviously that boost is way too low for a ported cobra and I'd bet my longtube headers and o/r midpipe don't help. I'm thinking that the car wasn't taking advantage of the ported blower at that psi. Shouldn't it be more like 16-17.5 psi?

No eaton's don't make 17.5 easily or efficiently or people wouldn't be buying twin screws. Your long tubes will drop boost too. When my car was ported and pulley'd (2.76 upper only) with stock manifolds I saw at most around 13.5 PSI. Hot days 12 was common. Your torque seems low though. Mine was 487/495.

wow that does seem kind of low
my car put down 478 HP and 503 trq on just a 2.76 upper only pulley non-ported
and of course exhaust, intake and tune
pretty sure that lower pulley is going to help a lot

That seems high for upper only car and not the norm of what most people see. Of course dyno numbers are just that. They can be made to spit out what ever numbers.

15.6 psi on a unported eaton isn't a common thing. The norm is around 12.5-14psi. Highest I've seen mine go is 13.5 on a cooler night.

Yup what he said.

 

[Mustang Matt]

They're just dyno numbers. They're fun to talk about but "different dyno, different day" makes them nearly useless for comparison to everyone else. Don't worry about them! Drive the car and enjoy it!

Quarter mile passes are the true comparison numbers.