Thanks.....my best pull was in PA with Exede, 279 whp 271 ft lbs. and were only running 18 psi, with exede i was running 21.5 ...we had a run that hit 309 whp but he wanted to have a perfect tune for everyday driving..Im done modding my car, ill be a mid 12 and ill smoke tons of cars on the street, now time to dress it up a bit, wheels/tires/springs/tint......then im finished....thanks Al!

 

Your torque would be higher with a 2.5"DP. Nevertheless,

 

What gear did you do your pulls in?

 

I got to ask 4bngr , why 2.5" =more tq?

 

2.5 inch dp will flow better in the low rpms creating more power, at the expence of top end power. the evos seem to make peak torque at around 3000-4000 rpms. thats pretty low. you can open up the exhaust, sacrifice a few ft lbs down low to extend and flatten the tq curve. IMO if you have a proper manifold and turbing housing a huge short exhaust will make more power everywhere. the evo turbo is pretty inefficent, thats why you see more tq with a small exhaust.

also keep in mind that bigger exhaust/dp will facilitate a faster spool up.

 

I have yet to see any conclusive proof of this

 

Don't bother let them be slower

 

Ive never have seen a dyno chart that showed a smaller DP makes more tq down low than a 3" dp . Iam sure the smaller tubing would make more down low on a NA motor but we talking about turbos. The peak TQ #'s come after the turbo starts to spool , so how can LESS flow help the turbo to spool faster to make more TQ ??

 

of what? which part have you not seen any proof of?

the exhaust flow stuff is simple engine theory, nuthing special there.

the fact that the turbo will spool faster is because the faster you get the exhaust gasses in and OUT of the turbo the faster the spool. if i had it my way everyone would run around with 3.5 inch downpipes exiting out the side of the car.

the last high hp honda i did had a precision sc61 (61mm, 56 trim compressor wheel, with 0.63ar t350 turbine housing with a 76 trim wheel.. supports around 650wheel hp) that spooled 28psi at 4800rpms, 16psi by 4400. its NOT a ball bering turbo, it has 270deg race bering and it has a 3.5 inch downpipe. other cars with similar setups dont spool that turbo till about 4-500 rpms later., everyone else uses 3 inch dp. that motor was 7.8:1 compression, 84.5mm bore, 89mm stroke. very similar in size to a 4g63

 

how much do dynoflash cost with the tuning on the dyno?

 

Of course

Originally posted by Wadzii
2.5 inch dp will flow better in the low rpms creating more power, at the expence of top end power.

This statement is what Im concerned with.

Or

Originally posted by Wadzii
the evo turbo is pretty inefficent, thats why you see more tq with a small exhaust.

???

 

i think its like 450 or 500 for dynoflash and Pruven costs 180 per hour on the dyno...tiny bit high for dyno time but they run a nice setup and are very good people to do work with...

 

exhausts are a matter of compromise. you can build an exhaust to work well at one specific rpm and it will merely be ok at other rpms. the exhausts job is to scavenge exhaust gasses and get them out of the motor. a small exhaust does this better at low rpms. it just so happens that peak tq on an evo occurs at low rpms. at high rpms the exhaust creates back pressure so the engine has to work harder to push the gasses out.

a big exhaust wont provide enough velocity at low rpms and the gasses just kinda sit there, creating back pressure. but at high rpms the exhaust can do its job and there is no back pressure and it works good.

where the turbo/manifold comes in. if you have a restrictive manifold and turbine housing then a big exhaust is just going to slow the gasses down too much when they come out of the turbo at lower rpms. a small exhaust ill keep the velocity up and get the exhaust away from the engine.

if you slaped a similar sized turbo on the evo with more efficent wheels then you will see that a 2.5 inch dp would be way to restrictive when compared to the rest of the system.

i always recomend 3 inch stuff b/c its more than likley that you will want a bigger turbo later on, and when you are up in the higher rpms, such as when you are doing a track event or drag racing the bigger exhaust will allow a MUCH quicker spool. it depends on your driving style. if you drive like grama and sit at 3000 rpms all day long then a 2.5 inch dp is good for you.... but then again grama dont have an evo. if you want to be fast, go racing, etc then you will relize that the higher in the rpms you make the power, the faster you will go.

 

A turbo is the "restriction" in the flow efficiency of an exhaust system and creates back pressure. Mufflers will not give any hp increase over a muffler delete pipe (they sound cool though)...
Buschur and Works have it right with their muffler delete pipes (I'd recommend that they fabricate a 3" muffler delete pipe for those who wish to go with a bigger turbo in the future)...

The Cat Converter is the other big restriction...

USING THE "STOCK" TURBO... Again, the STOCK Turbo...

All things being equal, a 2.5" DP will produce an exhaust gas that is less dense than a 3" DP. This is because the 3" DP diameter allows the exhaust gas to cool and become more dense than the 2.5" DP.

Exhaust gas is a pulse and you don't want your engine to be pushing a heavy mass of exhaust gas out of the tailpipe - this causes torque loss. Maintaining hot exhaust gases that are less dense allows for more efficient expulsion and better torque over the 3" DP.

MP5-

I've been pressing Dave @ Buschur to do a comparison dyno of 2 stock turbo cars by way of asking for dyno figs for his Econo stage, to no avail. All things being equal, I bet the torque figure would be higher than on the Stg. 1 car using the 3" turbo back.

4-BNGR

Anyone have a stock Evo out there with 3" turbo back and 2.5" turbo back

 

4-BNGR, I think you and me are probably in the same boat regarding the 2.5" dp/md combo.

HELLLOOOOOO BUSHUR.... we really really want to see it .... and no were not kidding....

4-BNGR, maybe we are going about this the wrong way. Maybe if we offer them some incentives.... like say.. some homemade chocloate chip cookies, steak dinner, or a Ferrari Enzo.. then might be willing to speed the dyno up.

Personally the theory regarding more torque on the 2.5" setup appears to be good (on a stock turbo that is), but we have no evidence (as MP5 has mentioned) regarding this.