Low boost readout

[Gabe]

I'm only seeing 6-7 psi on the in-car gauge when WOT, with very brief spikes to 8psi.

A run-down of car's mods:

Gauge is a digital AEM unit.
Blower is 2.3L Whipple with the 9-psi 3.25" pulley.
Car has JLT 123mm CAI, ID1000 injectors, 2 catch cans also installed, and the small sections of the stock exhaust mid-pipe have been cut out and replaced with non-mandrel-bent 3" pipe. The resonators were also replaced with 3" pipe, and the car has 11-12 GT500 mufflers.

So why am I not seeing 9psi on the gauge?

Running a JDM tune, their answer is that the engine is using the air being pushed into it so it doesn't get built up in the lower manifold enough to create the pressure to read 9psi.

When I first got my tune/blower installed, running 275/40/18 tires, the car put down 591 rwhp on the dyno.

I recently went to a dyno day at the same shop, and with the new exhaust mid-pipe "mod" done and the new catch cans being the only changes, running 305/35/20 tires it put down 546 rwhp

The tuner did a quick datalog and said the car was running 20% lean at idle but looked OK otherwise.
The lean condition was thought to be from a slightly loose-fitting catch can connector on the driver side, the one going to the intake tube.

Where did my power and boost go?

 

[stkjock]

the new exhaust mid-pipe "mod" done

better flow = less boost to make same power

as far as the power difference, ~7.5%, both corrected to SAE? what's the weight difference of the rim tire set up? 20"s will eat some dyno #s

 

[Gabe]

I heard that about the exhaust "mod", and yes, both were SAE-corrected.
Unfortunately, no idea about wheel/tire weights

The 18" was an SVT 18x9.5 cast aluminum wheel, with a Continental DWS 275/40/18 tire
The 20" is an AMR 20x10 with Nitto 555R 305/35/20 tire.

The 18" was 26.7" tall, the 20" combo is 28.4"

 

[stkjock]

my bet would be a good part of the delta is the wheel tire package. more weight and farther from the axle

 

[rcm90]

Do you have any dust around the belt? 45whp is way to much to be a change in tires. The mid pipe change can lower the boost, but I would expect power to pick up just a bit because IAT's should be a touch lower. The "spikes" in boost make me think its slipping a little.

When was the last time the dyno was calibrated? Take the car to the track, it never lies.

 

[Mystickeith50]

Do you have any dust around the belt? 45whp is way to much to be a change in tires. The mid pipe change can lower the boost, but I would expect power to pick up just a bit because IAT's should be a touch lower. The "spikes" in boost make me think its slipping a little.

When was the last time the dyno was calibrated? Take the car to the . ack, it never lies.

I agree. The only first hand knowledge I have is I lost about 1 to 1.5 psi when I put longtubes and off-road exhaust. I then gained some back with a bigger throttle body. Unless your losing boost due to belt slip(which is sounds like that could be the case) you shouldnt be losing power necessarily because boost is really an indicator of restriction basically .

 

[Department Of Boost]

When I first got my tune/blower installed, running 275/40/18 tires, the car put down 591 rwhp on the dyno.

I recently went to a dyno day at the same shop, and with the new exhaust mid-pipe "mod" done and the new catch cans being the only changes, running 305/35/20 tires it put down 546 rwhp

How long between these two runs?

 

[Gabe]

Thanks for the replies and trying to figure this out with me guys ...

Do you have any dust around the belt? 45whp is way to much to be a change in tires. The mid pipe change can lower the boost, but I would expect power to pick up just a bit because IAT's should be a touch lower. The "spikes" in boost make me think its slipping a little.

When was the last time the dyno was calibrated? Take the car to the track, it never lies.

No dust around the belt, other than the typical dust/dirt inside the Whipple pulley.
Belt feels tight.

How long between these two runs?

Almost a year.

 

[Department Of Boost]

Almost a year.

Then the data is mostly irrelevant.

 

[Gabe]

OK, just had another Dyno Day with my Mustang Club.

I put down 545 rwhp, 478 rwtq.

Latest things to be done to the car were the removal of the driver side catch can, replacement of the stock H-Pipe with the 3" JBA H-pipe which shrinks to 2.75" at the back of the pipes so it mates up with the stock pipes.
I also installed Lethal's 2.75" mandrel-bent over-axle pipes, and installed JLT's PCV valve inline with the PCV hose that comes from under the blower and connects to the Tee that then feeds into the catch can and into the blower.

Car's still running the same JDM tune that put me at 591 rwhp, 505 rwtq with this 3.25" pulley.

Local tuner guy thinks the car is no longer adding timing like the tune was doing for the 591/505 run where the knock sensors added timing to a max of 17.5 degrees, which my local guy always thought was too much for the stock Coyote bottom-end.

I always thought that the 10-psi 3.25" pulley would put me at close to 600 rwhp, which apparently it did, ONCE.

Last April I was in the 540's, and again today the same lame results.

Anybody have any thoughts?



.

 

[rcm90]

Fuel could be inconsistent. Also have you done a compression/leak down test? Again, dyno's vary from shop to shop. The only real way to tell is by taking it to the track to see what the car traps.

 

[Department Of Boost]

I always thought that the 10-psi 3.25" pulley would put me at close to 600 rwhp, which apparently it did, ONCE.

Last April I was in the 540's, and again today the same lame results.

Anybody have any thoughts?

Not trying at all to be a dick. Just giving the opinion of someone who has done a massive number of A-B-A tests in their time.

Standing way back and looking at no data aside from what is in the quote one would surmise that the 600hp run was some sort of fluke and the other two are more representative of reality.

It is only a sample size of three though.

Additionally 550hp seems to be the number for 10psi on a Yote.

 

[Gabe]

Haven't done any compression tests, the car runs like a raped ape, other than the numbers aren't what I expected anymore.

And DOB, I guess I'm just a bit surprised about the 550/10-psi thing ... I thought I'd seen enough Coyotes putting down close to 600 rwhp with the 10-psi pulley ... guess not?

 

[BruceH]

Are the pulls being done in the same gear? It can make a difference. More than likely the first one was a hero run that just won't be repeated. You could always run a smaller pulley, lol.

 

[Gabe]

Are the pulls being done in the same gear? It can make a difference. More than likely the first one was a hero run that just won't be repeated. You could always run a smaller pulley, lol.

Always done in 5th gear, the 1:1 MT82 gear

Plan right now is to install the 40a KB bap I just bought, a bigger TB and a 3.125" pulley, and have the local guy re-tune it, since I've kinda lost faith in the JDM tune.
It seems that it has too many variables built into it.
The local guy doesn't let the knock sensors add timing, he keeps blown Coyotes to 14 psi I believe, and zeroes-out the adders, while letting the PCM still remove timing if needed.

 

[BruceH]

Always done in 5th gear, the 1:1 MT82 gear

Plan right now is to install the 40a KB bap I just bought, a bigger TB and a 3.125" pulley, and have the local guy re-tune it, since I've kinda lost faith in the JDM tune.
It seems that it has too many variables built into it.
The local guy doesn't let the knock sensors add timing, he keeps blown Coyotes to 14 psi I believe, and zeroes-out the adders, while letting the PCM still remove timing if needed.

Most tuners do exactly that. Sometimes an adder can get missed because it's labeled as a retarder but can still add. From what I've heard about tuning a Coyote it has more adders and tables than the 3v has and it's fairly easy to miss something.

I'm wondering why the bap? Is the fuel pump having trouble keeping pressure?

 

[Stephen31201]

I have a 10lb pulley and show 6.5 on the gauge. Originally it was at 9.5 psi, but the long tubes and pro chamber mid pipe free'd up the restriction. Take this for what its worth, but "tuners" are a dime a dozen, and a sign and a dyno hardly make for a good tuner. These guys make a fortune because most end users cant tell the difference. I recommend you message Lilto that's on this board. I would also recalibrate the A/F gauge (takes 10 mins) just to be sure its reading correct.

 

[Department Of Boost]

And DOB, I guess I'm just a bit surprised about the 550/10-psi thing ... I thought I'd seen enough Coyotes putting down close to 600 rwhp with the 10-psi pulley ... guess not?

I see a whole lot of bullshit out there when it comes to Coyote HP numbers.

This HP thing has gotten way out of control in the past 10yrs. Back in the day no one knew how much power they were making so they figured out how fast their car was by racing it.

Now there is a dyno on every corner and most people race dyno graphs on the internet. The problem is made worse by the industry now using dyno numbers as advertising. Bullshit/fudged/tweaked/leaned on in ever way dyno numbers. The interwebs and magazines are not at all representative of real life.

550hp is a lot of hp. Go drive your car and have fun.

I have a 10lb pulley and show 6.5 on the gauge. Originally it was at 9.5 psi, but the long tubes and pro chamber mid pipe free'd up the restriction. Take this for what its worth, but "tuners" are a dime a dozen, and a sign and a dyno hardly make for a good tuner. These guys make a fortune because most end users cant tell the difference. I recommend you message Lilto that's on this board. I would also recalibrate the A/F gauge (takes 10 mins) just to be sure its reading correct.

Lito doesn't tune Yotes.

he keeps blown Coyotes to 14 psi

You can't run a Yote at 14psi on 93. Well, you can. But it will knock all over the place and pull all the timing out. And eventually you will hurt parts.

The limit is 10.5-11psi unless you run better fuel.

If you want more power de-restrict the motor so boost drops then add back in blower speed till you're at 10.5-11psi.

 

[Gabe]

Most tuners do exactly that. Sometimes an adder can get missed because it's labeled as a retarder but can still add. From what I've heard about tuning a Coyote it has more adders and tables than the 3v has and it's fairly easy to miss something.

I'm wondering why the bap? Is the fuel pump having trouble keeping pressure?

The datalog that was done after the 3.25 pulley and its tune were installed showed the fuel pump duty cycle at 96% when WOT over 5,000 RPM.
So I want to add the BAP to be safe there, especially since I want to add a bit more power

You can't run a Yote at 14psi on 93. Well, you can. But it will knock all over the place and pull all the timing out. And eventually you will hurt parts.

The limit is 10.5-11psi unless you run better fuel.

If you want more power de-restrict the motor so boost drops then add back in blower speed till you're at 10.5-11psi.

I meant to write 14 degrees, not psi.
The local guy said even 15 degrees is a bit too much, when he saw my logs showing 17-17.5 degrees he really started shaking his head ...
Part of the reason I want him to re-tune it.
He's known for always providing safe tunes.
May not get you the numbers you're looking for for that dyno printout, but the car will run great and be safe doing it.
He originally tuned my car when it was N/A with the only mod being an Airaid CAI, his tune put me at 405/387, numbers I was very happy with, at the time, and the car ran awesome.
JDM's rep I dealt with told me he had basically the same set-up as me and he was around 590 rwhp, so obviously I wanted the same dyno numbers, when I had the same mods.
I got it, originally, but a year later the car "relaxed" to the 545/475 range.
Now I feel duped, since I have to buy/install MORE parts to get back to the numbers I was at right after I bought their tune.

 

[Kobie]

Have you checked your bypass valve? If it is hanging open, even a little bit, you will loose boost. Worth a look?