Low boost readout

[JeremyH]

I can easily see a tire wheel change effect dyno numbers, seen it many times.
For some reason low profile street tires tend to yield the best numbers. Higher side wall street tires and things like softer ply of dr's or bias tend to eat some power.

Also another thought, if you have a smart tuner, your car usually wont ever make the same power it made on the dyno when tuned. It's a lot easier to put up higher numbers when doing tuning. Once you hit that number you want, most tuners pull a half degree to a degree of timing and add 1-2% fuel overall for safety and real load on the street, or with passengers in the car etc.


Belt slip and boost bypass are good things to check, also the gauge itself or line to the gauge etc.

I wouldn't get to hung up on numbers. Even when I made 650 and then 760rwhp its fun but I enjoying driving the car the most on lower boost settings 550-600hp range.

 

[Gabe]

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

I have not.
What's an easy way to check it?
Just manually work it open/closed, and see if it goes all the way in both directions?

I can easily see a tire wheel change effect dyno numbers, seen it many times.
For some reason low profile street tires tend to yield the best numbers. Higher side wall street tires and things like softer ply of dr's or bias tend to eat some power.

Also another thought, if you have a smart tuner, your car usually wont ever make the same power it made on the dyno when tuned. It's a lot easier to put up higher numbers when doing tuning. Once you hit that number you want, most tuners pull a half degree to a degree of timing and add 1-2% fuel overall for safety and real load on the street, or with passengers in the car etc.

Belt slip and boost bypass are good things to check, also the gauge itself or line to the gauge etc.

I wouldn't get to hung up on numbers. Even when I made 650 and then 760rwhp its fun but I enjoying driving the car the most on lower boost settings 550-600hp range.

Yesterday's run was done on 18" DR's, 305/40/18 to be exact.
They've been weighed and they're about 1 pound lighter than the 305/35/20's I had on the car last April when I first started being disappointed with dyno numbers.

Also, the tune I'm running, I loaded after I installed the 3.25 pulley, had the car datalogged locally, sent the file to JDM and they said it's fine, just drive/enjoy the car.
They never sent me a revision which might have the changes in it that you mention.
So of course I expect my car to put down similar #'s next time I run it. Wouldn't you?

Check for belt slip ...a year ago you were on a brand new belt ....they wear and slip after time especially a daily

I will definitely have to do that.
I had somebody video the boost gauge during the dyno run yesterday, and watching it a few times it does seem to be dropping a bit at higher RPM:




The dyno run video:

 

[Department Of Boost]

I have not.
What's an easy way to check it?
Just manually work it open/closed, and see if it goes all the way in both directions?

If you're seeing your max boost all the way through the run your bypass is fully closed.

Yesterday's run was done on 18" DR's, 305/40/18 to be exact.
They've been weighed and they're about 1 pound lighter than the 305/35/20's I had on the car last April when I first started being disappointed with dyno numbers.

It's about sidewall compliance/tire softness (sticky) far more than it is about weight. Those DR's are a LOT more compliant and sticky than your street tires.

Also, the tune I'm running, I loaded after I installed the 3.25 pulley, had the car datalogged locally, sent the file to JDM and they said it's fine, just drive/enjoy the car.
They never sent me a revision which might have the changes in it that you mention.
So of course I expect my car to put down similar #'s next time I run it. Wouldn't you?

You would expect it to. But there are a 1001 variables that can add up to the discrepancy you're seeing. Dyno's are not "variable proof". Not even close. Trans/diff/oil temps all by themselves can constitute a 25-35hp swing with no problem at all. Then there is the tire change which can be 10hp. Then add in a slight IAT difference for 5hp. And you're getting real close to the difference you're seeing. And I just put up the easy examples. There are a lot more.

I had somebody video the boost gauge during the dyno run yesterday, and watching it a few times it does seem to be dropping a bit at higher RPM:

Which one is the boost gauge? It's hard to tell? The top readout on the bottom gauge? As far as I can tell it is holding boost fine at 11ish. Or am I seeing something wrong? No coffee yet!!!!

The dyno run video:

I was at Walsh Motorports (Donnie Walsh). Last week. We were looking at a graph from a Yote he had in the day before to see how it compared to ours which was on the dyno. At 10psi with a Gen2 TVS guess what it made? Yep, 547hp. Guess what our car made (before the clutch started slipping)? Yep, 551hp at 10.5psi.

I hate to bum you out man but I think you have a 550hp car there and the big number you saw was some sort of fluke.

 

[Gabe]

Which one is the boost gauge? It's hard to tell? The top readout on the bottom gauge? As far as I can tell it is holding boost fine at 11ish. Or am I seeing something wrong? No coffee yet!!!!



I was at Walsh Motorports (Donnie Walsh). Last week. We were looking at a graph from a Yote he had in the day before to see how it compared to ours which was on the dyno. At 10psi with a Gen2 TVS guess what it made? Yep, 547hp. Guess what our car made (before the clutch started slipping)? Yep, 551hp at 10.5psi.

I hate to bum you out man but I think you have a 550hp car there and the big number you saw was some sort of fluke.

The top gauge is the boost gauge, oil psi is below it and was showing near 100 psi or more during the run (it flat-lines at over 100 since the gauge only goes to 100)


Looking at maybe changing out the belt since it's got about 10k miles on it now ... the Gates belt that came with the kit is 83 1/8" long. Could/should I do a belt that's slightly shorter to get more pressure on it? They list one at 82.5" long ...

 

[Department Of Boost]

The top gauge is the boost gauge, oil psi is below it and was showing near 100 psi or more during the run (it flat-lines at over 100 since the gauge only goes to 100)

Gotcha, it was bouncing around so much I couldn't tell what was going on with it.

I wouldn't put too much trust in that gauge. It shouldn't be bouncing around that much, even if the best is slipping. I kid you not I come across incorrectly reading boost gauges ALL THE TIME. In my experience your chances of having an incorrectly reading gauge is about 50%. No shit.

There is an old saying that I picked up while racing/testing/doing development work.

"If you have one gauge you know what your XXXXX is. If you have two gauges you have no fucking idea."

This is because more often than not if you hook up/use two different gauges reading the same thing you will get different readings between the two. And boost/vac gauges are notorious for this.

Looking at maybe changing out the belt since it's got about 10k miles on it now ... the Gates belt that came with the kit is 83 1/8" long. Could/should I do a belt that's slightly shorter to get more pressure on it? They list one at 82.5" long ...

This is a very complex situation to solve if there is an issue. Belt/tensioner systems are not simple.

Can you snap some pics of your tensioner with the belt on? I'm not familiar with what that kit came with (or what you're using).

Then remove the belt and measure total tensioner travel. This can be rough-ish. Within 1/4" is fine. Then put the belt back on and measure where the tensioner is in it's travel. Is it 25% of the way in? Is it 50% of the way in? Is it 75% of the way in? This is all very important stuff. You can't just go throw longer/shorter belts at it until you know where it is running at right now in regards to travel and spring preload. You could easily make the situation worse.

 

[BruceH]

I'm not sure if it's been mentioned yet but do you know the density altitude of the different dyno days? DA can affect boost by a few psi. In fact when boosted people blow motors it can be due to a nice cold winter day providing that few extra psi that the fuel system, tune, or motor isn't ready for.

 

[Gabe]

I'm not sure if it's been mentioned yet but do you know the density altitude of the different dyno days? DA can affect boost by a few psi. In fact when boosted people blow motors it can be due to a nice cold winter day providing that few extra psi that the fuel system, tune, or motor isn't ready for.

Looking up historical weather info, and calculating it for the fairly close NH Epping track , the DA looks to have been about -1472

Yesterday's DA comes out to -46

 

[BruceH]

Looking up historical weather info, and calculating it for the fairly close NH Epping track , the DA looks to have been about -1472

Yesterday's DA comes out to -46

I think you have it right there. At least part of it. Both days were good hp days but -14xx is huge.

 

[07 Boss]

The top gauge is the boost gauge, oil psi is below it and was showing near 100 psi or more during the run (it flat-lines at over 100 since the gauge only goes to 100)


Looking at maybe changing out the belt since it's got about 10k miles on it now ... the Gates belt that came with the kit is 83 1/8" long. Could/should I do a belt that's slightly shorter to get more pressure on it? They list one at 82.5" long ...

Can't you adjust for belt length? The whipple should have that little idler pulley that is in the slotted hole. I have mine set so that so that I have to push my tensioner arm all the way down to get the belt on. It might be slightly tight but it only chirps occasionally when I do a low pressure 2nd to 3rd gear shift and it shifts slow.

 

[Department Of Boost]

The 3v and Yote kits have completely different belt setups.

 

[07 Boss]

The 3v and Yote kits have completely different belt setups.

Oh yeah, I keep forgetting where I am at. You would have thought that they would have put in some kind of adustability in it though, no?

 

[Department Of Boost]

Oh yeah, I keep forgetting where I am at. You would have thought that they would have put in some kind of adustability in it though, no?

Could be, maybe. That's why I asked for pics.

 

[Johnf78]

Why was the boost gauge on the Dyno screen reading correct for you GF's car but not yours? Was yours not hooked up to the Dyno?

Oh and don't catch a lane along side the old lady! Lol

 

[Gabe]

I think you have it right there. At least part of it. Both days were good hp days but -14xx is huge.

Yeah that's a big difference, but 50 rwhp and 30 rwtq worth?

Why was the boost gauge on the Dyno screen reading correct for you GF's car but not yours? Was yours not hooked up to the Dyno?

Oh and don't catch a lane along side the old lady! Lol

Lol ... I read this out to her and she was dying laughing ... lmao

My car's using an electronic boost gauge and the signal "probe" is screwed right into the manifold so the tuner couldn't hook up his boost/vacuum hose to my car.
Slightly different set-up on the GT500 so he hooked it up there

...

Can you snap some pics of your tensioner with the belt on? I'm not familiar with what that kit came with (or what you're using).

Then remove the belt and measure total tensioner travel. This can be rough-ish. Within 1/4" is fine. Then put the belt back on and measure where the tensioner is in it's travel. Is it 25% of the way in? Is it 50% of the way in? Is it 75% of the way in? This is all very important stuff. You can't just go throw longer/shorter belts at it until you know where it is running at right now in regards to travel and spring preload. You could easily make the situation worse.

The tensioner on this kit is freakin buried.
It's behind a huge bracket, the belt wraps around it twice:

Sorry I don't have a better pic but as you can see, it's almost impossible to see the freakin thing.

I even tried a video:




And then a video showing the belt tension, and I zoomed in on the belt grooves to see that it looks good, at least to me, doesn't show like it's been slipping:

 

[Department Of Boost]

The tensioner on this kit is freakin buried.
It's behind a huge bracket, the belt wraps around it twice:

Sorry I don't have a better pic but as you can see, it's almost impossible to see the freakin thing.

That's the Roush designed setup. That's a good setup for the Yote. A real PITA to see what's going on though.

Order this and check your belt tension. This is the best way to make sure you know what is going on by far.

Amazon.com: Gates 91107 Belt Tension Tester: Automotive@@AMEPARAM@@http://ecx.images-amazon.com/images/I/31pvKGIxD7L.@@AMEPARAM@@31pvKGIxD7L

 

[Gabe]

That's the Roush designed setup. That's a good setup for the Yote. A real PITA to see what's going on though.

Order this and check your belt tension. This is the best way to make sure you know what is going on by far.

Amazon.com: Gates 91107 Belt Tension Tester: Automotive

Yup, Roush kit.
Ford Racing apparently cheeses off that kit when they sell one with the Whipple head unit on it, with the Ford Racing decal on the blower.

Just ordered that tension tester.

The blower belt is the same one that came with the kit that normally uses the 9-psi (3.375") pulley, so there's a good chance (I think) that I could use a slightly shorter belt, now using a 3.25" pulley

 

[BruceH]

Yeah that's a big difference, but 50 rwhp and 30 rwtq worth?

A -1472 DA is pretty good. I'm going to guess it would add at least 1psi, probably more. Add into that how the correction factor affects the numbers and I think it accounted for at least part of your increased numbers.

Atmospheric pressure at sea level is 14.7psi, at -1500 feet it's 15.5. I don't have a formula to see what effect it has with a supercharger but it's going to be more than the .8psi difference felt in the atmosphere. I think the super low DA accounted for most of your increased hp.

 

[Department Of Boost]

Yup, Roush kit.
Ford Racing apparently cheeses off that kit when they sell one with the Whipple head unit on it, with the Ford Racing decal on the blower.

Just ordered that tension tester.

The blower belt is the same one that came with the kit that normally uses the 9-psi (3.375") pulley, so there's a good chance (I think) that I could use a slightly shorter belt, now using a 3.25" pulley

The key is to get the tensioner in the right part of the travel (basically 50%). Here is some info on tensioner setup:

http://departmentofboost.com/tech_instructions/belt_tensioner_tech.htm

You can double check it against the tension on the belt. Find one of the Gates Fleetrunner (green) belts if they have them in the right size, they're really, really good. I won't use anything else.

You should have no problem getting that all dialed in. That is a good tensioner setup.

 

[travelers]

I was going to check mine but the belt tensioner is for V belts. That's how old it is.

 

[Department Of Boost]

I was going to check mine but the belt tensioner is for V belts. That's how old it is.

I don't understand?