david fracolli

Actually a cam would make more difference that a chip. With a cam you shift the tourque curb up and take advantage of the better high end breathing capabilities of the head.

hosrom_951

Doesn't CFM mean more power? more air flow=more power generally speaking?

I mean, if the car was completely stock, then the money is just wasted, spending that money would benifit for MAP/MAF, WG etc right? or am i wronge here?

If that is the case, then when would a modified cylinder head really help out in dyno number?

david fracolli

I think people are looking at this the wrong way. You can increase HP without increasing torque. One of the biggest problems with a stock turbo head is that torque really starts to drop off after about 4500 RPM's.
Now let's assume the car is generating 300 ft/lbs of torque at 4500 rpms but drops to 270 by 5250 RPM's. If you could shift the torque curve up so that torque at 5250 RPM's is now 300 instead of 270 you have just gained 30 horsepower.
Would a ported head work on a completey stock engine....yes but not to it's full potential.
To realiaze the full gains of a ported head though, you must also have a cam that matches the flow characteristics of the head.

hosrom_951

David: Thanks for the info. Regarding the "Would a ported head work on a completey stock engine" statement, i asked because certain mods work together, as in when starting to mod a car, you don't just go and get a ported head and cam.

What i mean is, doesn't it all depend on the power goal your aiming? say 400whp? you could get it w/o the head work right?

Basically, what im trying to ask is at which level should one consider this kind of modification? Basics are chips/injectors, MAP/MAF, WG, exhaust and so on.........

alexands

Porsche-O-Phile: What, exactly, is a Callaway 951? Are you doing something with the guys that tune Vettes? Just curious. What are the details?

Thanks,
Scott

BC

I looked on the site. No price? No info?

Porsche-O-Phile

It's a Callaway turbo conversion kit for the n/a 944 - I'm using a 951 head since it has the ceramic-coated exhaust ports and sodium-filled valves capable of withstanding the extra heat generated with a boosted engine. Less to go wrong, ultimately. There were only 32 such kits produced by Callaway - it was an extremely lucky find on my part. I should be able to generate 300 rwhp when all modifications are completed - not too bad for an "n/a" car. . . Of course the early cars are lighter too

B951S

So the Callaway kit turns an N/A into a 951 minus the right brakes and suspension????.....I hope it's a lot cheaper than just buying a 951 and doing some 'regular' mods.

Porsche-O-Phile

Kinda yes. It was a conversion that Callaway Engineering came up with shortly after the release of the 944 in 1983. They saw the potential for the platform to be downright incredible performance-wise given its handling and drivetrain and developed the kit as a way to turn the early 944s into world-class competition cars, similar to what they do with Corvettes and other respectable "starting" platforms. The conversions were not cheap at the time either.

Basically it entailed decreasing the compression ratio from the stock 9.2 or 9.1:1 to 8.0:1 to better handle the boost using special pistons (remember, there were no 951s in the world yet). The setup uses a microprocessor controller and fifth injector (mounted in the intake plenum) to detect and prevent over-lean conditions. The turbocharger itself is mounted directly off of a custom-made exhaust manifold with the turbo hanging off the bottom and the wastegate on the top. An intercooler sits behind the lower air dam getting its cooling air from the "low" ducts there.

My particular kit lacks the Callaway microfueler controller and pistons; I am instead using 951 pistons since they provide the same 8.0:1 compression ratio, are Porsche-original (and tested) parts, and are available. I'm sure the ones that were originally installed by Callaway in whatever car my kit was originally in have long since worn out. The microfueler is an MF2 on mine also; it uses newer technology and circuitry than was available in 1985 (so some might consider it "cheating", but I don't see it that way). It still uses all the rest of the original components: oil pan, turbocharger, wastegate, intercooler, piping, plenum, etc.

Eyal 951

it is cheaper... and the NA DOES have benefits over the turbo... lighter and such... he has the callaway car and a 951, best of both worlds!
As for the head, You shouldn't expect info on his sight just yet. Once mine is done, and on the car, there will be dyno numbers posted, as well as more information based on what danno would like to release. I am not matching the head work with a cam at the moment, and it was not suggested/mentioned me to do so...
~Eyal

OriginalSterm

does any of the headwork you are having done increase compression ratio? if so, how are you planning on doing something to prevent knock with that crappy CA gas?

or do i just not understand what "head work" really entales?

Eyal 951

danno will work the map so that even with raised compression, it can still run on oh-so-crappy 91.. I've seen him able to tune a modded 944 turbo to run on 89 with NO knock or anything, he knows what he's doing.
~Eyal

OriginalSterm

i don't doubt he knows what he's doing, but if the knock is dialed out by retarding timing, that hurts performance.

i'm anxious to see what kind of gains a head job nets. i have absolutely no idea.

Eyal 951

well, of course id see better performance on 93 octane, but not an option here.
~Eyal

OriginalSterm

91 + toluene (or xylene) and maybe some marvel mystery = alternative