Petevb

Anyone know the functional differences?

The Cup motor is making ~400 claimed hp, though you can bring this up with an exhaust.
The World Challenge motor is quoted at 445 hp. As i understand it the extra power mostly due to the GT3R manifolds and plenum, but perhaps the "sprint specs" include internal motor changes (of the kind that would hurt longevity)?

Is one motor heavier, or otherwise preferable to the other, class/ rules aside?

Thanks for any info- I'm looking to understand the differences before I put some money down...

-Pete

Johninrsf

One is double the cost of the other when you figure 40hrs. vs. 80 hrs. TBOH.
Actually, it's almost triple: a rebuild for the Sprint motor is about 35K and for the Cup motor, it's about 25K, so the sprint motor costs approx. $875/hr and the Cup motor about $312/hr.
The important question is how are you going to use the car --to race? with whom and what Class? to DE?

Petevb

Good info- the sprint motor costs more to overhaul because they used more expensive (lighter) internals? The sprint motor runs a higher compression ratio too?

The car is an outlaw- nationals level autocross and DEs/ time trials primarily. I certainly don't need the last 5 (or 15) hp, but I do need low end torque.
If I went with the sprint motor I'd be looking at reducing the redline rpm to increase time between rebuilds. I've been told by some engine builders that time at idle/ street speeds don't count towards engine life whatsoever, and basically the last 500 rpm is where all the damage is done... To what extent that's true I don't know.
I wonder if, come rebuild time, PMNA can "update" the internals with the longer wearing parts?

If the prices were equal I think I'd go cup for the longevity sacrificing power. If the cup is 35-40k (complete w/ ecu, etc) and the sprint motor is ~25k also complete, both low hours, it seems a harder choice...

jrgordonsenior

I think you've got your costs backwards....

Johninrsf

Yes to both questions above. I think the particular longevity problem is with 2 ring pistons in the sprint motor vs. 3 ring in the Cup.
I'm still trying to figure out who you're going to run with and in what Class (even as a Time Trialer).
You may be going way beyond what's necessary for what you want to accomplish.

Petevb

Almost certainly going way beyond what's necessary... It's not really about "need". From a practical point of view the ~340 hp air-cooled motor I've got in the car now is good enough for 95% of what I want to do, easier to class, etc...

The costs are not backwards, but the cup motor is an '06 vs the '02 WC motor.

Geoffrey

I think there is some misinformation here.

In 02, the RS engines ran 3 ring pistons and higher compression than the cup engine (I think 12.5 vs 11.5 or somewhere in that range), the same length conntecting rods as an 06 cup, but larger camshafts. The speedvision engine did not run individual throttle bodies, but rather a modified Cup intake that removes the dual plenum and is converted to a single plenum by welding the two pieces together, and is controlled by a single throttle body. I believe it used the 02 RS pistons and cams.

Petevb

Thanks for correcting me, Geoffrey.
It's sounding more and more like the cup motor would be better for me- the lower compression would be nice for tuning to a wider range of gases (I will need to put 92 in it at one race in particular, at least) and the dual plenum intake and milder cam would probably both help low end torque.

The lower cost of the WC motor still makes it attractive, though. I wonder if, come rebuild time, they would "de-tune" it to more like the current cup spec for a reasonable price? I also know someone with a full carbon RSR intake on the shelf- attractive from a weight point of view if nothing else...
Or perhaps mixing and matching parts is a bad idea?

Geoffrey

I would have no problem running any of the water cooled GT3 engines on 93 octane fuel at 12.5:1 compression or lower using a programmable engine management system like MoTeC. Don't forget that the 02 and earlier cup engines specified fuel that is about the same as 93 octane US fuel, in fact, I know people running 02 cups on 93 fuel. Given a choice of induction system, I would choose the GT3R,RS,RSR individual throttle system over the Cup or speed world challenge intakes because the engine will always run better, and always make more power, and I like the speed world challenge intake over the stock cup. There are many combinations and permeatations of these engine that can be built, and with a programmable engine management system, you are not limited to the combinations provided and supported by PMNA.

gmgracing

World Challenge spec engines are siginfigently more in terms of costs and rebuilds.

There have been several different "versions" of WC engines . It really depends on which engine you have.
The electronics and tuning on the WC engines are different as well.

The engines are signifigently different.

WC engines are tuned for 98 octane fuel and I would not run them on anything less than that octane rating.

We have both at the shop.



Fabryce
GMG

World Challenge Speed GT Team

JW in Texas

Hey Pete,
Did you get my pm last week?

944CS

Fabryce,

Are these old WC motors that you have? I know Groom had to ship his back to Germany right after the last race of the '06 season.

Jerseybean

Who told you that, I dont think John shipped anything out....

944CS

One of the engineers helping Jon out