Why round exhaust pipe?

[dieselgeek]

Based on my experience: if *anyone* can show up and bring +5hp to a Pro Stock engine program (density altitude being equal) - that is a relatively huge deal.

[TC]

Based on my experience: if *anyone* can show up and bring +5hp to a Pro Stock engine program (density altitude being equal) - that is a relatively huge deal.

That's what happens when you race dyno's and not cars....... 5hp on a prostock isn't shit........... I just showed you that...... In reality they probably need another 10-15hp(and it might be higher than that) to go .01 seconds faster.......

[TC]

If you dont think so, your kidding yourself..... forget that calculator

In all due respect, I am forgetting the calculator..... Put it this way I've never seen a car run what a calculator says it will run, the cars always run slower...... So I figure in a perfect world if it takes a prostock about 8hp to increase it's speed by .01 seconds that in the real world it's going to take more than that to achieve that same increase...........

[MR P-BODY]

I dont plan on getting in a pissin match with you BUT P/S cars
actually play in .001 instead of .01 so figure what it takes then...
does it figure out to a lesser number.... and those numbers change
day to day just on the weather... when your on a dyno it makes X
HP per those conditions of the day

[dieselgeek]

Put it this way. I know of a top shop who spent $30,000 over the winter working on a valve seat design that picked up 2hp and this was only for their Stock Eliminator program. Pro Stock is working in even smaller increments, and yes - Pro Stock engines are developed and tested on a Dynamometer.

Just because it's not in someone's post on a mustang forum waiting to be plagiarized, doesn't mean it's not true. It just means that TC doesn't have access to any better data. Wallace Racing calculator? LMAO.

[TC]

I dont plan on getting in a pissin match with you

Neither do I with you...... Like you said other variables play in the game...........

[MR P-BODY]

Going back to your calculator ... being that it shows.... .66(I think it was)
is that a .661.. or a .669... you see that makes a major difference thats
not shown... so like you said... you have to discount some of the variables
but believe me the P/S guys are looking for every little edge they can find
be it in the engine or chassis

[JeffMcKC]

TC will argue with himself given half a chance, has anyone showed you the ignor feature on the site yet? Pro Stock, Comp live to gain 5 HP TC its a heads up race there is nothing to small at that level they dont just stumble on 15 HP thats been over looked its 5 here 2 there.

[dieselgeek]

TC will argue with himself given half a chance, has anyone showed you the ignor feature on the site yet? Pro Stock, Comp live to gain 5 HP TC its a heads up race there is nothing to small at that level they dont just stumble on 15 HP thats been over looked its 5 here 2 there.

I tried ignore but it killed the entertainment factor. I'll switch it back on when I'm in Serious mode. hahahaha

[jcharliem]

I tried ignore but it killed the entertainment factor. I'll switch it back on when I'm in Serious mode. hahahaha

The entertainment factor has always been there with TC - actually, it's always on "tilt." He makes such bonehead, clown comments. I don't believe he's ever been on a track other than his keyboard-track. Always states some lame-ass comment, only to change to something else. The latest being his statement that 5hp ain't going to amount to spit. Laughable.

[yellomalibu]

Iin ANY heads-up form of racing, I agree with the majority here: ANY extra power is an edge. Like Jeff said, it's unlikely that any of them are going to stumble upon 15hp from one thing within the existing set of rules they are following. 2 here, 3 there, and it adds up over time to give one team an advantage.

I also agree with TC in my belief that the faster you go, it takes exponentially (he said percentage) more horsepower to see similar gains as it did to get to where you are now. I have no science or computer program to back that up - but I don't think that's what people are disagreeing on.

[JeffMcKC]

If a Pro Stock right now had 25/30 HP on the feild, he would be King ( Allen Johnson ring a bell right now)

[jcharliem]

...it takes exponentially (he said percentage) more horsepower to see similar gains as it did to get to where you are now...

It is exponential. Yet, the point is... put more power to the pavement, then you're gonna be faster. 0.5 or 30. Doesn't matter how much, as long as it's a positive amount. More = Faster. To make statements that an increase - regardless of how little - won't make a difference is simply ignorant.

[dieselgeek]

It is exponential. Yet, the point is... put more power to the pavement, then you're gonna be faster. 0.5 or 30. Doesn't matter how much, as long as it's a positive amount. More = Faster. To make statements that an increase - regardless of how little - won't make a difference is simply ignorant.

Exactly right. If Stock Eliminator teams are spending tens of thousands of dollars for 2-3hp, it's a big deal to them.

When we got 7hp out of one of these engines versus another EFI box, there was a lot of celebrating going on. And some butthurt other EFI vendors too. lol

[CDMBill]

Minor data point. At SIR in Tucson last night I pulled the exhuast after several baseline passes. I was pedaling the launch a bit as the track was hosting an import event and I couldn't launch hard on that drag radials. My 60 ft's are normally in the low 1.40's and here it was 1.60+. But, the net was from an average ET around 10.33 the times dropped to an average of 10.15. Average MPH only changed from 135.5 to 137.2.

The exhaust is 2.125-2.25" step headers with short primaries (30" avg.) into a 4" merge collector out to 3.5" oval frame tubes to a round tube 3.5" Dr. Gas (RIP) x-pipe. From there the full system is a taper down to 3" tubes into 3" DynoMax welded Ultra flow over the rear end to 18" DynoMax bullet reasonators and 3.5" rolled tips.

I add the detail as the change was to a set of 4" dumps angled out right after the x-pipe. I rolled across the tracks scales before and after and saw 4153# and then 4051# with the exhuast removed and four passes run off a full 20 gallon tank. The car uses a bit over a gallon per pass. The exhuast weighs 70#, so the net benefit with a little tuning, not complete as it showed lean, was slightly less than .2 seconds at 6000' DA of which a tenth might be attributable to the 100# of weight dropped between the exhuast and fuel load.

My theory has been to gradually reduce the diameter of the exhaust over its length after the x-pipe to maintain velocity as it cools and shrinks in volume. I'm not sure if I'm happy that the full system seems to be pretty efficient or that I didn't pick up more from taking it off. Sounds good to me though.

Your results may vary.