K R.....!!!

Any ways..... I'm just after my KR.....!!!

Quote :

So basically all your statements are irrelevant with the original statement which was smaller to larger to smaller exhaust piping makes HP, which is what this "tech" discussion started as.

You can think that, but then why do so many people see immediate gains (and lower KR) from swapping to just a 3" DP and nothing else? Common logic would show that if you gain from a 3" downpipe, why would you want to use a 2.5"? That's not much different from OEM.

I would still argue that if I'm using headers with totally stock cat-back, stock T-split, stock mufflers, stock everything... If the stock pipes were so restrictive, why aren't these gains being erased? Sure, the pulses are better aligned with headers, but if the pipes can't flow, that shouldn't matter, right? HP is about flow. How did I run a 3.2" SC pulley with a stock exhaust system, minus cat, plus headers?

Exhaust is most restrictive close to the manifold, less as it moves back and cools. Downpipe bend is where the system is choking to breath before the rest.

Turbo is a different game with totally different rules.

Rick, this conversation is mildly relevant, because you will normally see KR with any pulley size under stock with that little DP on there.

I agree 3.0 is better..... But at the time they could not bent me a 3.0 DP...it kinked...... and I needed it quick , for a drive clean.......so 2.5 , I got..... Having no cat helps.....
Anyways .... It ran strong with just the stock DP and 3 inch cat.
and now, it lost some snap.....!! I will look into the injectors...

How did they bend the DP? Mandrel bend machine?

Don't k now..........

That's kind of a key aspect of pipe bending. Mandrel bender results in smooth bends, and is preferable for exhaust. Most small shops can't afford a mandrel bender; I think that's one reason the DP vendors have a successful business.

info: http://www.hoganperformance.com/about_our_products.htm

[quote="AA"]

Quote :

So basically all your statements are irrelevant with the original statement which was smaller to larger to smaller exhaust piping makes HP, which is what this "tech" discussion started as.

AA wrote:

You can think that, but then why do so many people see immediate gains (and lower KR) from swapping to just a 3" DP and nothing else? Common logic would show that if you gain from a 3" downpipe, why would you want to use a 2.5"? That's not much different from OEM.

^ Well the oem one have kink's and horribly designed. You keep wording everything around differently. Maybe i need to refresh your memory. The argument was for 2.5" dp Vs. 3" dp with the same bends makes HP with stock manifolds and catback. It WASN'T 3" vs stock will see less KR.

AA wrote:

I would still argue that if I'm using headers with totally stock cat-back, stock T-split, stock mufflers, stock everything... If the stock pipes were so restrictive, why aren't these gains being erased? Sure, the pulses are better aligned with headers, but if the pipes can't flow, that shouldn't matter, right? HP is about flow. How did I run a 3.2" SC pulley with a stock exhaust system, minus cat, plus headers?

^Its not always about how much flow you have. With your case you have a blower so there is too much flow with everything on a factory exhaust.

AA wrote:

Exhaust is most restrictive close to the manifold, less as it moves back and cools. Downpipe bend is where the system is choking to breath before the rest.

^Not arguing that.

AA wrote:

Turbo is a different game with totally different rules.

^correct

AA wrote:

Rick, this conversation is mildly relevant, because you will normally see KR with any pulley size under stock with that little DP on there.

^won't benefit, you will be wasting your money. Rick you should really get headers, or at least a plog.


This thread is full of miss-information. I won't even bother arguing it anymore because its not worth my time. Bottom line it a 3" dp bolted on with a totally stock exhaust won't see any HP gains compared to a 2.5" dp with the same bends as the 3".

Okay, anyhow let's get back to the original problem.

We need more information about the loss of power - a full scan would be needed to evaluate running conditions. I'm not sure what other reasons there might be for partial boost except maybe a bad tensioner and some belt slippage?

Hey.... guy's I'm just after to lower the KR......
and I know , I will get some..... It seems better today......
I tried a different Gas station..... Before I was using Shell......
Now went back to Sunoco....
I know Shell has less octane....... But , it was alot colder then......
See how it is, when it gets warmer...
perhaps I'll do another Seafoam .... but use it through the
injectors

99prixgt wrote:

AA wrote:
Exhaust is most restrictive close to the manifold, less as it moves back and cools. Downpipe bend is where the system is choking to breath before the rest.


^Not arguing that.

That's all I was really trying to say. You agree with what I'm saying, so let's move on. It's not mis-information, it's two different opinions. There is more than one (your) way to solve a problem.

For everyone's reference, here is ZZP's opinion:

"Stock downpipes are double-walled tubing with an inside diameter of just over two inches. Following the restrictive downpipe section, the stock unit subjects the exhaust gases to the choking effects of the catalytic converter. After the cat, it flattens out into a section dubbed the infamous "U-Bend," which is a section of pipe crushed into a "U" shape by GM in order to fit a rear O2 sensor. This section has less volume than the same length of 2" pipe, and approaches the volume of a 1.75" pipe with the rear O2 sensor in place! Our downpipe eliminates all of the aforementioned problems! Gains of over 15HP have been seen, along with a substantial drop in knock. Most users can drop a pulley size and/or eliminate 5-7 degrees of knock. This part can typically be installed in under an hour.

2.5 inch downpipes are designed for naturally aspirated applications where no loss in low end torque is desired. They can also be used in supercharge applications when the lowest possible cost is important. They come with interlock flex standard."

Did you check motor mounts? Also where is your IAT located? did you clean your MAF sensor? Is your intake shielded from engine bay heat?

You want a 3" DP no matter what. 2.5" is what the NA guys use.

There's a bunch of things it could be that we mostly gone through in this thread. Go through all your general maintenance items first and then you can play with the tune. Your FPR could be the culprit as well. My car's KR went away when it was stock after changing the FPR.

edit: I read a few more posts in here and agree that headers are the way to go if you plan on going with more than mild mods. Manifolds should be good down to a 3.5" pulley though... of course, every engine is different and I've seen some go all the way down to a 3.4" with no KR.

Yes .... Maf was cleaned.... IAT is in stock locatation
I have a modded stock air box...... header wrap on crossover..
and this was happening in the winter.... here in the great white
north... .................................................................................................. Last year in the winter It would change lanes
from troque steer and loss of traction from a 20 mph roll.....

AA wrote:

99prixgt wrote:

AA wrote:
Exhaust is most restrictive close to the manifold, less as it moves back and cools. Downpipe bend is where the system is choking to breath before the rest.


^Not arguing that.

That's all I was really trying to say. You agree with what I'm saying, so let's move on. It's not mis-information, it's two different opinions. There is more than one (your) way to solve a problem.

For everyone's reference, here is ZZP's opinion:

"Stock downpipes are double-walled tubing with an inside diameter of just over two inches. Following the restrictive downpipe section, the stock unit subjects the exhaust gases to the choking effects of the catalytic converter. After the cat, it flattens out into a section dubbed the infamous "U-Bend," which is a section of pipe crushed into a "U" shape by GM in order to fit a rear O2 sensor. This section has less volume than the same length of 2" pipe, and approaches the volume of a 1.75" pipe with the rear O2 sensor in place! Our downpipe eliminates all of the aforementioned problems! Gains of over 15HP have been seen, along with a substantial drop in knock. Most users can drop a pulley size and/or eliminate 5-7 degrees of knock. This part can typically be installed in under an hour.

2.5 inch downpipes are designed for naturally aspirated applications where no loss in low end torque is desired. They can also be used in supercharge applications when the lowest possible cost is important. They come with interlock flex standard."

HAHA don't even get me started with zzp. Zzpee also says a smaller pulley is the best first mod...

AA im not trying to be an a-hole here, you seem like a cool guy. I just can't see why you would use a 3" DP, when you could use a 2.5 with the same free flowing bends. Thats it I am done.

Well don't worry you'll find plenty of us arguing and recommending against doing a pulley drop first. I did the pulley first, years ago, and have been recommending against it ever since.