My 2.9L Whipple SC

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ken sampson

Experienced Member
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10 November 2003
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I wanted to start updating my progress on my 2.9L intercooled Whipple SC.
Our number one goal was to control the boost. We managed to do this with the standard Comptech BOV. Now we are running about 10 PSI on the low end and 18PSI after 4200RPM. I will put together a diagram of this for anyone interested. After getting my boost under control I wanted to try my new Blox custom built DBW TB. It is a 76MM or 78MM TB. Once we put this on the car it became a totally different car. We ran out of fuel Injectors at about 5800 RPM. This was at about an 89 percent duty. I had RC 750,s they are now for sale.
I will post more later today.
 
Sweet!

Looking forward to more info.

Did you end up using a boost controller on the bypass valve? If so, did you intentionally limit boost at lower rpms or does it just build from 10psi up and you cut it off on the top?

- Craig
 
Last edited:
The boost can be anything from 8 PSI up to the SC limit. This can come in at any RPM level. We just shredded two belts on the Dyno so I am waiting on another belt now. My tuner just ordered two Kevlar reinforced belts.
 
750cc injectors with a turbo is enough to make 650 whp if you have the flow from the pump to supply it. The difference is that a supercharger requires more fuel if you measure whp because of the loss of hp to produce the supercharged pressure. (approx. 1/3 of the gain in hp is used to produce the pressure in a supercharged application) To show a 100hp gain in a supercharged car actually requires approx. 133 hp to show 100. That is what the supercharger used to produce the boost 33hp. This is only an estimate but this is why a turbo car requires less fuel to produce the some hp as a supercharged car. Not my opinion, just simple physics.
 
brian campbell said:
750cc injectors with a turbo is enough to make 650 whp if you have the flow from the pump to supply it. The difference is that a supercharger requires more fuel if you measure whp because of the loss of hp to produce the supercharged pressure. (approx. 1/3 of the gain in hp is used to produce the pressure in a supercharged application) To show a 100hp gain in a supercharged car actually requires approx. 133 hp to show 100. That is what the supercharger used to produce the boost 33hp. This is only an estimate but this is why a turbo car requires less fuel to produce the some hp as a supercharged car. Not my opinion, just simple physics.
Click to expand...

Oh, I get what you're saying, although given your numbers, you mean 1/4, not 1/3 (of the 133hp additional produced at the crank, 25% or 33hp drives the blower and the other 100hp (75% of 133) shows up at the wheels.

Also discussed in this thread:

http://www.nsxprime.com/forums/showthread.php?t=142574

I think your estimate (somewhere around 25% to drive the supercharger, perhaps a tad more) is about right.


My question about running out of injector is based on the fact that if I had to throw a dart as to what an 18psi SC motor would make at the wheels I would guess 550 - 575ish. That means given the losses to drive the SC, it's really adding 300hp(ish) to the wheels, plus requiring 100ish to run the blower, so it's comparable to a 650 - 675hp turbo motor.

Which, as you say, should be about out of injector.

BUT, I'm puzzled why the injectors would be at ~90% duty cycle at 5800rpm.

Unless:

1. The Supercharger requires significantly more than 100hp to drive
2. The motor produces significantly more than 550hp
3. The SC tune requires significantly more fuel than a comparable turbo tune.

All of which don't seem likely enough to me, which is why I'm puzzled.

No simple physics for me, just opinion and wild speculation at work :wink:
 
ken sampson said:
Remember i am using a 2.9L thats 1/3 more air per rev.
Click to expand...

Er, that shouldn't matter as I doubt both blowers would be spinning at the same rpm. Given the same manifold pressure, both blowers (any for that matter) will be supplying the same amount of air (assuming the same discharge temp).

Ultimately the motor can only be supplied with as much air per revolution as 1/2 the swept volume of the cylinders, albeit compressed air.

Unless of course you are putting that extra air somewhere other than your motor. :biggrin:


Hurry up with those new belts, it's exciting to see you back up and testing!


- C
 
Ken,

First let me say thanks for selling me your old factory headers. They worked fine for my turbo project.

What are you goals for your project? Sick street car? Track car? What is your hp goal?

Thanks
 
My goal has always been 500RWHP. I could have reached that with the 2.3L SC but when I needed to replace an IC o-ring Whipple talked me into going with the 2.9L. The car is for the street it drives and runs like a stock NSX until well you know:biggrin:

My tuner just called me he found my problem with the pulleys my SC pulley is missing a 060 spacer I made to align everything so he is making me another. He is also going to drill small holes in my pulley under the belt to allow air to escape and help reduce the lifting of the belt.
 
ken sampson said:
My goal has always been 500RWHP. I could have reached that with the 2.3L SC but when I needed to replace an IC o-ring Whipple talked me into going with the 2.9L. The car is for the street it drives and runs like a stock NSX until well you know:biggrin:

My tuner just called me he found my problem with the pulleys my SC pulley is missing a 060 spacer I made to align everything so he is making me another. He is also going to drill small holes in my pulley under the belt to allow air to escape and help reduce the lifting of the belt.
Click to expand...

Just curious, what was Whipple's rationale on using the 2.9 over the 2.3?
 
Dustin just said you know we have a new 2.9L that will bolt right up don’t you.
That’s all it took. When we spoke more about this he said it would take very little effort over my 2.3L to turn. However flows more than 30 percent more air per Rev. so I said ok I’ll take one.




DucatiCraig said:
Just curious, what was Whipple's rationale on using the 2.9 over the 2.3?
Click to expand...
 
I am going to change out the single port air bypass valve actuator for a dual port. This will give us more flexibility with boost adjustment. Plus I had ordered it not knowing if we would be able to use the single port. If my belts come in today I should be able to put it back on the Dyno.
 
Ok, that makes sense on the blower sizing, if it displaces 30% more air with < 30% more parasitic drag, then you will lose less HP to parasitic drag than with a 2.3l.


The dual port actuator bolts right in; it's a piece of cake :wink:

Since it does have an internal spring, there is a minimum amount of boost it will need before it cracks the bypass valve open. It will be interesting to see what boost pressure that is. I did some bench testing with a hand pump, and my guess is around 5psi.

The one piece I haven't finalized is the venting of the boost / vacuum lines to the actuator, as one side needs to see only vacuum, and the other only boost, otherwise the pressure / vacuum on each side of the actuator diaphragm will be the same, and it won't ....um... well, actuate.

I think if you pick up the vacuum from the intake snout that side will be fine and function just as it does in a comptech (er, CT engineering, er, SOS,..et al) kit as it won't see boost and will open the bypass under part throttle.

As far as the boost side, you will need to pick that up from the manifold, and do something to keep vacuum out of that line, and also to vent it when vacuum is trying to move the other side of the actuator diaphragm.

I think a solenoid to vent the line under vacuum coupled with a check valve will do the trick.


Good luck, can't wait to hear more!
 
Given you were at 470hp with the 2.3l, another 50hp from the TB would certainly put you at your 500hp goal :biggrin:


I thought this thread had some interesting points on TB sizing in relation to air velocity:

http://www.nsxprime.com/forums/showthread.php?t=129937


Interesting though that your previous setup had 28psi(!) of manifold pressure sucking through the stock TB, so the SC was getting the air through there one way or another :eek:. You probably did have some vacuum in the intake snout, but again, it didn't show up as a lack of boost pressure.
 
ken sampson said:
The link below shows the drive by wire TB Blox built for me it is a 72MM. I believe this change alone was worth atleast 50HP. This larger SC needed more air.

http://www.nsxprime.com/forums/showthread.php?t=123255
Click to expand...

If this is limiting the amount of boost than it will help.
May only be an issue at higher revs.

If you don't gain any boost pressure the only other effect it may have is reducing the vacuum on the inlet side of the supercharger. This may have and effect on the mount of power required to spin the blower.
 
I'm not sure. I do know as soon as we changed the TB we needed a lot more fuel. This is when we ran out of injectors. I'm sure we had a lot of VAC.
I will know more on Monday when it goes back on the Dyno.
 
DucatiCraig said:
Given you were at 470hp with the 2.3l, another 50hp from the TB would certainly put you at your 500hp goal :biggrin:


I thought this thread had some interesting points on TB sizing in relation to air velocity:

http://www.nsxprime.com/forums/showthread.php?t=129937


Interesting though that your previous setup had 28psi(!) of manifold pressure sucking through the stock TB, so the SC was getting the air through there one way or another :eek:. You probably did have some vacuum in the intake snout, but again, it didn't show up as a lack of boost pressure.
Click to expand...

I think I understand this little better now. We had the PSI all along however we never had the air volume. The stock TB was not keeping up with the SC.
If it warms up enough today we will be able to do a few pulls.
 
ken sampson said:
I think I understand this little better now. We had the PSI all along however we never had the air volume. The stock TB was not keeping up with the SC.
If it warms up enough today we will be able to do a few pulls.
Click to expand...


Good luck on the dyno today - Exciting stuff for sure! :smile:



I'll keep laboring away try to get my "little 2.3l whipple that could" done.

hmmmmm...lemme get the old slide rule out... okay... how does that go again.... um, P1V1 = something like P2V2.... er.. :confused:
 
Re: My 2.9L Whipple SC Update

We finally made another pull. The RWHP is now at 511RWHP at 7600 RPM. He lifted before we made it to 8K RPM. My tuner set this up with a three position rocker switch mounted in the ash tray. 1st position is around 6 PSI not sure on the second but the final is at 16 PSI. The switch controls boost.
This was a pull in 4th gear and it smoked the tires at 70MPH when he nailed the throttle.

I will post more later today.
 
where did you get the adapter to get that whipple to mounted up?
 
Ok I just received a copy of the Dyno run. My tuner said he will need to do a pull in the spring time to get my real number. The tires were spinning too much on this pull. I'm happy with the 511RWHP shown but he thinks it will show 550RWHP if we can get the power down to the Dyno. He also let off at around 7600 from what he said. He also estimates the FWHP to be around 690

About the intake to bolt the 2.9L I had built it from sheet metal.
 

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