Hey guys/gals just looking for some info. and opinions/answers on the topic at hand. A little background to this is I rebuilt a GSR, took it in for dyno tuning open header and the tuner told me he wouldnt touch my unless it had an exhaust on it. he said it throws off the tune too much. I found this strange since I had him tune my LSV turbo open downpipe. So I connected my Apexi WS2 and got it on the dyno. It made 174whp 128tq. I had thought it would be a bit higher...about 10whp higher.

82mm GSR block
GSR crank, rods and PR3 pistons (11.4:1)
B16 head w/ 00' ITR cams on S2 gears
Stock TB & IM
RMF narrow header (2.5' collector)
Yowaii SS intake
Magnaflow hi-flow cat
Apexi WS2 catback
B16 tranny w/ streetlite flywheel

I have done some searching and many people have been saying the WS2 exhaust with its 2.25" pipe is restrictive and causes major powerloss at high RPM (which I saw) and w/o it people were seeing 8-12whp gains. My cams stopped making power at 8k (I have seen graphs with them making power to 8500 numerous times) and dropped power from 8k to 8.5k

Heres my issue: I do plan on taking this car to the track and I know open header I will have better performance. Should I re-tune it w/ the exhaust off or will it GREATLY hurt me to run an open header tune on an exhaust bearing car for a daily grind?
Any input on this greatly appreciated and anyone with Info. on the WS2 reducing performance chime in as well.

Thanks,
Andy

 

could have had him do a tune both ways (then used a 2timer to switch between programs)....but better yet who the hell is he to say he wont tune your car open header? your the paying customer i would have tuned it however you wanted.

 

I have thought about piggybacking the ECU to do that but im not the electronic guru when it comes to cars, it the build, swap, and mechanic. I trusted the guy since Ive had 4 different motors tuned by him. I just havent been pleased with the tune though, I feel like the powerband is all messed up for an ITR style motor.
I expected at least 180whp and 130tq with this build and if what I have read its VERY easily attainable.

 

Bump for the night.......

 

Morning fellas....Bump

 

that exhaust is pretty hard on power numbers, i'd drop it and take it somewhere else...i'd upgrade ur cams too, easily a 200whp car with a dropped exhaust and cam upgrade.

 

So tuning the car open header then running an exhaust for DD wont hurt it? I am looking for the most output at the track. Ill sacrafice numbers on the street to stay below the radar.

I will be building my top end this summer.
Skunk2 Pro1's
Ferrea complete head kit (6000 series fat faced valves, dual VS and Ti retainers, bronze valve guides, upgraded lockers and keepers, high temp valve seals)
BBK IM w/ portmatched 70mm TB

My goal with that is 200+whp with the WS2 on, I need to keep the car quiet the cops in my area are ***** on modified exhaust.

 

From personal experince, i've tuned my own car through a exhaust and then dropped it and ran it.. shouldn't have a problem with it..but if you want max power, then yes.. i'd tune it..

 

My biggest beef is my ITR cams stopped making power at 8k which is not right. They should make power to 8500....this is why I think the exhaust is choking me at higher rpms, so in theory a open header tune will allow for better a/f at top end correct? With the exhaust on it may run just a hair rich which im fine with.

 

I think you should upgrade cams personally

 

Just out of curiosity.. Who tuned the car?

 

Why to you think ITR cams make power to 8500rpm?

I am running ITR cams, 11.5:1 compression and a custom 2.5" exhaust. I would have to say 7500-8000rpm is my peak and very typical of what I have seen on other builds.

Do you have a dyno to post?

 

You have a nice header on what is about an 82mm itr motor. Slightly higher compression, but less airflow (b16 head/IM/TB). Numbers look on point to me.

 

Skunk2 Pro 1's are in the works

James at speedfactory here in WA. they have some killer cars so I would assume I have a good tune...he knows his stuff

My dyno sheet is back at home, im at school til december, so I can't post it right now. My buddy has a GSR w/ ITR cams and on the dyno it carried power up to 8300... I figured with my compression and B16 IM over the GSR it would carry power at least that high.
Can you share the specs of your build with me? you made 15whp more then me on what looks like an identical setup.

I have seen similar builds get 180+whp on just a base tune like the one above

 

The only reason I could see him not wanting to tune your car open header would be because o2 sensor placement on the header, but I know for a fact there's still like a foot of piping if not more after the o2 on the narrow copy, so I have no idea why he wouldn't tune it open header.

 

Yea the collector pipe is about a foot long and the O2 sensor is at the front of it so it should not get false readings due to outside air obstructing exhaust gasses exiting. That is why I was confused....I have seen MANY cars tuned open header or even open downpipe for that matter.

 

I would ask James what he thinks would make more for you.. He is one of the best tuners I know. He will tell you strait up..

 

...who doesn't tune open header........i mean really.

 

I asked him what he thought of my numbers and he thought they seemed OK. I asked him if the exhaust made a big difference and he said open header the tune would be too far off. (I still want an explanation on this) He was in the midst of getting his car built/running the same day so I think his attention was focused elsewhere and less on the fine details. No disrespect to him but I paid $300 and havent been completely satisfied with the tune. He didnt set my 2 step, didnt set my CEL shift light, didnt change to my 4bar map sensor I provided and wouldnt do it open header. I realize hes a busy guy but all of those are maybe 5 extra minutes of work.

 

You think I should get an open header tune and go from there? Im not trying to seem optimistic but I think 180-185whp is definately the range of power I should be looking to get with a good tune. I mean STOCK itr's put down my numbers with less compression/smaller bore, no intake/performance header, stock exhaust and all that jazz.
Its tuned on Crome Pro if that changes anything.
Im not saying hes a bad tuner, hes not, but I feel like something is off somewhere and until ican get some reassurance I will always feel that way.

 

going from a restrictive exhaust to open header will throw off the tune...you need to have it tuned both ways....or leave the exhaust you have now and do a cutout and have it tuned with the cutout open and closed.

 

if he isnt worried about what it does on the street then tune it on the dyno without the exhaust. When you put the exhaust for street driving (given its a 2.25" or chambered bolt on cat back...something that will actually choke the engine) it will be richer than what you tuned for on the dyno. If you only race at the track then it wont matter. Leave closed loop enabled for the street and the o2 sensor will take care of the difference during part throttle.

 

Makes sense. I mean the differences cant be THAT HUGE to the point my car is going to run terrible with the cat-back on. It may get slightly worse gas mileage but its not like it will be overfueled to the point of failure to burn fuel.

 

not at all.

 

Alright guys problems solved When I get a chance Ill get it retuned open header and hopefully see my goals of 180-185whp. Ill be building the head this summer as well.
Thanks