Oddjob

But there is less load, since there is no wind/air resistance, correct? I know when I had my car dynoed it rev'd out 4th gear a lot faster on the dyno, than it would actually driving through the same rpm range on the street or track.

special tool

Some types of dynos can make the load, Jim.
It is probable that you were on a dynojet 248c model.

Oddjob

Yep, it was a dynojet.

If other types do have increased loading, then I absolutely agree that an afternoon of pulls on a dyno would be tougher on a car than street driving, since the little fans (they set in front of the car) do not push enough air through the radiator and intercooler to simulate 100+ mph.

jimbo1111

A dyno jet will do that but a mustang loads the car with wind and weight as factors. Very close to actual road conditions. You can even load the car continuously at a certain speed or factor in a uphill grade.

M758

Still one dyno pull is less stress than one lap on race track.

Why? Each acceleration on a race track is just like on dyno pull. Consider however that the dyno pull only lasts one gear.


I just ran at PIR this weekend so consider this track at only 1.5miles vs dyno pulls.

Starting at Turn 9 (slowest part of the track).

Mid corner speed is 35 to 40 mph. As soon as I hit the apex it is full throttle. 2nd from 4700 rpm or so to 6200-6400. Then 3rd to 6200 rpm, full throttle. Then 4th to 6400 rpm, then 5th at about 5000 gaining only tiny bit to may 5400 rpm. Seems to me this just like 3 straight dyno pulls.

Then touch the brakes and back to full throttle for turn 1. Down**** to 3rd for turn 2. Part throttle/throttle steer to apex. Then full throttle again from about 4000 rpm right to 6200 rpm and into 4th. Full throttle again to ... we I am busy to figure it well. Anyway touch the brakes and turn then right back full throttle for 1-2 seconds.
So 2 mory dyno pulls, for 5 so far.
brake hard and downshift to 3rd. Give part throttle till the tires hook up at maybe 3500 rpm and then give her all she has rev her to 6200 rpm again. one more dyno pull. Then up into 4th. Take her to 5000 or so and brake hard for turn 9.

So even in a short 1.5 miles I figure I did 6 dyno pulls. Consider each lap ticks by in 1:13 to 1:15. Then consider that 30 min race can cover 20+ of these laps. So in 30 min that is some 120 dyno pulls. Then figure that on any one day you do 4 sessions. So a track day has the equvalent of some 400 dyno pulls. The really astonishing thing is to do 120 dyno pulls in 30 minutes. Tell me that is not stressfull.

Oddjob

I agree with Joe.

I strongly believe that engines are subjected to much more adverse conditions in racing than they are when driven on the street. For example, even with stock power, a 944T club race engine is going to last 10-20k miles before needing a rebuild. A street engine will last 100-150k w/o needing any mechanical work (these numbers are arguable, but I wanted to toss out some ballpark figures for discussion’s sake).

My home race track is Brainerd International. It’s a 3 mile road course, with a 5000 foot front straight. For a 944T, you go through 3rd, 4th, and into 5th down that straight. Approach turn 1 at approx 140-145 mph, don’t even hint at lifting, pedal dead to the floor through 1 and approach 148-150mph going into turn 2, which is a lift, and a slight tap of the brakes, back on full throttle and carry approx 120-125 mph through the turn and a short straight until braking hard for turn 3. So for a 944 Turbo, the car is at full boost for nearly a mile and half w/o let off, and for over 2 miles with just the letoff for turn 10 and turn 2. And this is lap after lap (over a full minute of an under 2 minute lap, for the length of the race).

The EGTs get high going down that front straight. This track causes a lot of burned valves and blown headgaskets for the 944T guys. Over the years I have seen many chipped and modified 944Ts (including some expensive engines) that will run all day long, for months and years, on the street with no problems, not last an afternoon at the track.

My belief is that:

You can build a 400 hp motor that will blow up in a street car or on the track (oops).

You can build a 400 hp motor that will be fine on the street but blow up on the track (street engine).

You can build a 400 hp motor that will be fine on the street and last on the track (race engine).

You wont build a motor that will blowup on the street, but work fine on the track (?).

And my feeling is that a motor that would be limited to 400 hp to be a reliable race motor, could probably be pushed to a reliable 450+ hp for street use.

My guess is that if you call some of the major/professional engine builders, and ask them to a quote a 400 bhp street engine, versus a 400 bhp full race engine, you will likely end up with two $ figures.

I know of guys that have spent around $30k on engine rebuilds for a 30-60 hour sprint motor. These are PMNA/Andial type engines for 993RSR 3.8's and 996 GT3RS's. They are expensive for a reason, and my point is that, you dont need to spend that kind of money to build an equal horsepower street use only engine.

Again, no need to question the hp numbers, I just tossed out some arbitrary horsepower figures for discussion.

porshhhh951

I have to agree with the stress levels of track use But, to be honest I ride the hell outta my car running 20psi all the time. I hit full boost all the time. I have done a couple rally's with the car now and I dont know what you guys do there but, here its pretty serious.

Last one was 250miles of hard boost/ cornering/braking. Its very very rough on you car and we claim several victims every time we do one. Peoples radiaters blow, hg's go, one guy had a oil pump failure and messed up his turbo and various other parts.

I say this because i have been running people several years ago claimed to be crazy un hered of boost levels and i have been doing it now for almost 3 years on this setup. Now to be fair how many track days has my car undergone-1. But, I run my car very very hard and I subject it to rally's, and highway pulls over distances at higher rates of speed.

I by no means take it easy on my car. Everytime I get in it I hit full boost 2 dozen times even if I just going someplace close. Boost is just in my blood.

I have yet to have any failures with my car other than a HG which was old at the time and I knew it was going to go out eventually.

porshhhh951

btw in no way im I saying that track doenst see alot more stress than daily driving. That would be crazy.

But, I think there is some mis information floating around about just how hard we do run are cars on the street and around town. Obviously its not tracking the car...heck lets be honest its not even close.

But, hell I havent had one major failure in 3 years! how do you explain that?

Oddjob

I dont doubt that you beat the snot out of your car on the street. Im just stating that racing is harder on a car than DEs, DEs are harder on a car than street driving.

If your car handles agressive street driving with no problems, maybe it can handle DEs no problem, and maybe it can handle racing w/o blowing up. And if that is true (if it can handle racing as is), then I propose that it can also handle more power for reliable street use.

porshhhh951

agreed

RolexNJ

Damn did this thread get twisted in every direction from what Duke posted it for?

Anyway, I just want to say that for extended periods of use on race engine, it is harder than on street engines. But I do think a "properly" tuned street engine that's also maintained well, as John is an example of, can last a very long time and still produce very high HP numbers. So can someone now please make 600 RWHP, glory run or no glory run, so we all can be excited to see what a 951 can do? I think 2006 will be a great year, and my hat is off to whoever the individual is that does it. Looking back, I have to commend ST for brining the 951 to the 500 RWHP + mark, and with minimal mods too.

God, I love these cars. We are old 4 banger cars, and yet are producing some incredible numbers with some nice areas under the curves that enable us to keep up with alot of today's fast & modern-day super cars. That is just awesome guys! Do I hear anyone bidding on 700 RWHP for 2007? Any takers?

Tomas L

Of course racing engines have a harder life and has to be build differently than street engines. Anyone stating otherwise is just kidding themself (I'm sure someone now will state that their street driving style is as demanding as race conditions). The almost constant use of full power will put a heat load in to the engine that you will not get when street driving. And the more power the engine has the more heat will be put in to the cooling system and engine compartment. Why do engine builders redesign coolant flow through the engine for powerful track engines but very few street engines need such mods?
I don't understand why people feel offended because there are higher demands on race engine. Since a street engine doesn't have to meet the same demands as a track engine, it doesn't have to be built handle those demands. It would be overkill and waste of money to build a race engine and then use it for street driving when you could build an engine that's equally powerful, and does the job it's required to do, for less money.

Another more subjective difference beween a race car and a street car seems to be that a street car is rated for what it "has" (666 rwhp, XXX turbo, etc...) while a race car is rated for what it "does" (xx seconds at track ABC). How many threads with acceleration or cornering figures do we have here in the 951 section? Compared to the rwhp threads I guess there is a 1:100 or greater difference...

porshhhh951

agree 100%

p.s. I dont think anyone would argue street stress is equal to track stress....and if they do they dont know what they are talking about.

For the record we are jealous of the rated at what it does threads. Atleast I am. I want track times for my car thats just plain cool, to really be able to take the car to the maxium limit and not have to be concerned with anything else is pretty much what its all about.

I hope to have the time and money to hit atleast motorsports ranch again this next year...and I would love a track road trip to several others in the US.

namly road atlanta/mid ohio/laguna seca

Duke

agree

Duke

sorry, just arrived at work waiting for my hangover to come...
Christmas along with all its Christmas parties is dragging me down