NZ951

Not in bed! Its lunch time! Good idea about the catch can... I need more space in my bay. What is a good spark plug gap with my set up? I have always been a little unsure...

Bri Bro

I did a little digging and found this article. My first reaction was that reducing the plug gap by that much was excessive unless you run the engine 99% of the time under high compression ratios (boost).
Ignition

The first order equation for Ignition voltage output is:

Vo = 6.66*Sqrt(d*S) + 24.44*d*S
: where: Vo = electrical strength of the gap
: d = Relative Air Density (RAD) versus Standard Atmosphere (STP)
:RAD is the combination of temperature, barometric pressure, and humidity
: S = distance between the electrodes (in cm)

This doesn't address different metals used in the gap or different gas mixtures for the air. It does show that decreasing the gap has a direct effect on Vout but compression preasure is measured as a ratio of relative preasure vs STP. I am just looking at the math, sorry to say you are way above anything I have had to deal with. My calculations would put the gap at 0.025 for a 17lb boost to keep the same Vo as 14lb boost. You stated that a gap of 0.022 would smooth out the problem. Did you try this?

Duke

Nice!!
It would be interesting to hear more about the how the car felt with the new versus old turbo.
I suppose spool up is reduced with lower A/R on the hot housing, but how about the top end pull?

Tomas L

Has anybody tried an air/water intercooler on a 951?
With the limited space we've got it could be a solution.
It should be possible to find room for the watercooler somewhere in the front or perhaps near the gearbox. Or you can use two or more smaller watercoolers.
It will add a little more complexity with a waterpump and plumbing but could worth the trouble.

Tomas

TonyG

Tomas L

I've researched it...

Air Water intercooling system are dependant on the volumn of water contained, and the pumping capability of the pump. The more the better...

Thus for a system to be worth anything (at least for track use) it's going to have a large radiator, and a high flow pump.

And with that we're back pretty much at square one... surface area/volumn for the heat exchangers.

The only non used area is in front of the front wheels, using the driving light duct. Perhaps a pair of heat exchangers for the air/water intercooler could be located there... thus saving having to build a customer engine radiator...

There's plenty of room in the engine bay fora serious air/water intercooler for sure.

TonyG

badcoupe

I used a air to water intercooler in the last turbo car i put together. Great for drag racing but I don't think it would last long enough for a track session. We had to drain and reice every to hours or so, approx 2 passes. after one pass most of the ice was gone and the water was just about 60 deg.

Matt H

TonyG - do you have the p/n from the plugs you were using? I need to order some and I believe you mentioned you were running NGK-R plugs but I dont remember seeing what plug number.
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TonyG

beab951

Your calculations really can't come up with a required gap setting based on boost. The boost measurement is taken at the intake plenum, and has zero bearing on what portion of that air actually makes its way into the combustion chamber, thus one car at 18psi boost can be making 300RWHP and the other making 400RWHP, which in this case, the density of the air in the combustion chambers of these two cars is night-and-day different.

What I have found out, through plain old dyno testing, is that around 375RWHP, the gaps have to come down to .028" At 400RWHP, the gaps have to come down to about .020" (stock ignition to stock ignition).

TonyG

TonyG

Matt H

NGK-R

BPR7ES

Gap them around .028 to start with.

TonyG

Matt H

Thanks, did you snag them at autozone or did you have to order them?
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Ben Z.

Napa had them in stock.

Matt H

Cool, will pick them up on my way home tomorrow!
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kasturbo

Tony, Wormhole posted this pic in another thread. Thought you might be interested as this looks like what you described doing to your car. Are you going to try to keep your front end looking stock?

MySwiss

Nice.

rhesus

*whimper*