binder

iTrader: (8)

ah, i didn't know you had a rev-up and i thought the most current numbers on sasha's car were with the things he has in it now.

Nismo exhaust has a full baffled muffler so i would think it to be pretty restrictive. My borla true dual didn't like anything over 500hp and it's supposed to flow pretty good. Baffled mufflers aren't good for FI. I wouldn't think it to be restrictive at this power level but ya never know. I guess it could be enough to require a few extra PSI to get the same results.

also, like stated before, no 2 motors are the same even if they came off the same assembly line. You said 10% difference in power and i've seen up to 15% difference in stock engines with no mods so it can happen. There are strong motors and weak motors out there just based on random chance from the factory.

smalmo1

iTrader: (2)

Good point Jeff. I guess it wasn't so much the difference but where it is on the chart. If it was down 10% across the whole curve it would make sense that the engine is a dog or the dyno is reading differently but to be nearly identical right up to 5k rpm and then the curve of the chart changes it led me to believe I'm "missing" power over a small % of the curve due to a problem/restriction.

I will book the dyno time for the weekend or next week and post the results with the muffler disconnected.

binder

iTrader: (8)

good point. I was just making a "matter of fact" statement without really looking at your graph. Dropping off after peak torque does appear like a restriction like you said. I would explore that route. I wouldn't get worried about an engine problem though.

maybe a user that had a nismo and went FI could chime in and add his thoughts on nismo flow.

djamps

iTrader: (1)

I was talking about 2.5" true dual... not single. I never wouldn't think of using a single exhaust on a VQ turbo setup.

My 2.5" dual makes 400whp easy WITH cats. If OP is running a single exhaust regardless of size thats the problem for sure.

binder

iTrader: (8)

single exhaust isn't too restrictive if it's a straight through muffler design.

My borla true dual was restrictive and it was dual exhaust. The problem was the baffled muffler. Guys with 3" single and straight through muffler are far better off. I run an exhaust cutout now but I truthfully think i could put a 3" straight through muffler on and pull great hp out of it. I just don't because I like my sleeper stock exhaust out back and I also stopped spending money on my car to conserve in my last year of grad school.

binder

iTrader: (8)

what does your timing map look like?

I'm curious what a "whisper of knock" is appearing as. Stock knock detection gives tons of false knock and with all the piping if there happens to be something that taps against the engine oil pan (charge pipe) then it will show up as knock as well. If he's pulling timing up top for the false knock that might be a reason for the flat hp.

konrad

iTrader: (15)

single 3" exhaust is more then enough for 400whp as long as its a straight flowing exhaust like a single exit none of that oem style mufflers
I made 415whp on 3" single with 2 resonators, and that was on a hx40 (50lb/min) flow

smalmo1

iTrader: (2)

Seb has some cool looking headphones to listen for knock but I'm not sure if he measured with the factory knock sensor or if he had his own knock sensor attached somewhere as part of that rig up. I would highly doubt he mistook a rattle for knock because pulling timing wouldn't have made it go away.

Boosted Performance

iTrader: (14)

Timing/tuning is not an issue here. These guys pulled 550whp out of the twin scroll 370z kit I built on only 9psithing (at peak HP). The more I think about it the more I think it is the nismo exhaust/muffler.

str8dum1

iTrader: (11)

unbolt the muffler and redyno. 10 minute job with a lift at a shop.

binder

iTrader: (8)

ya if he listened for knock then it probably was knock.

smalmo1

iTrader: (2)

Ran at the track last night but ran on 275/35R19 Hankook Ventus V12 Evo at 32psi. MT ET Streets were not in yet for my 16" wheels.

Best run was 13.5@109 - 2.2 60'. Highest trap run was a 13.7@113 - 2.3 60'.

I continued to have the hesitation issue randomly. Out of 6 runs it probably happened 4 or 5 times, not always in the same gear.

I'll go back to the dyno after I install a Blitz EBC set at 9 psi to see if that solves the fluttering/hesitation issue and I'll have the muffler unbolted to see if that stops the power from flatlining over 5k rpm.

Hopefully I'll have the ET Streets and the new dyno/exhaust done for next Friday at the track and can post some strong dyno numbers and time slips.

binder

iTrader: (8)

wastegate flutter won't cause the car to hesitate. The wastegate spring doesn't often flutter much if any. Tial springs are pretty solid. When it flutters it would only fluctuate a slight amount so boost won't drop of significantly so it would just feel like the power flattens out and not a "hesitation" where the car would stall out.

get logs and see what is going on. You really can't figure anything out until you have logs of what is going on with everything to see if the car is cutting out, misfiring, knocking, etc. You will see wastegate flutter real easy on a boost log. If it's a true hesitation like you describe it then i doubt it's wastegate flutter.