Power Loss at Elevation

krazynismo

I finally paid off my 370 Nismo so started acquiring parts looking forward to a dyno day. unfortunately my dyno dreams were not met by the output numbers.

let me start off with the mods i have.
Z1 cold air intake, Z1 high flow cats, Z1 upper and lower ported plenum, JWT C1 camshaft, DC sports stainless headers, 2 piece front and rear Akebono rotors.

some of these i installed myself (CAI, plenums, rotors) but had the shop install the headers and camshafts, and high flow cats. i am located in salt lake city where we only have 91 octane and the elevation is around 4,500ft.

the above parts only put down 305whp and 237wtq. the base run was 276whp and 236wtq.

these numbers suck! for the money i would have been much better off running a nitrous kit and keeping everything else stock. so here are my questions.

1) does anyone else have experience with NA motors at higher elevations? from what i have read for NA motors there is around a 3% power loss for every 1000ft. theoretically this would have put down around 347whp (not sure if torque loss is the same) at sea level still on 91 octane. ive read you can pull another 8-10hp from using 93 octane so that would have put me around 355whp (assuming 15% drive loss this would be just over 400hp at the crank). this makes sense because the parts i have pretty much match Z1 400hp package (test pipes, headers, ported upper).

2) how much will running E85 instead of 91 help? i see around 14whp gains and lots of low end torque on the forum but i think that is mostly compared to users who were on 93 octane.

3) similar to running E85 i think my next step is a nitrous kit as i want to put down at least 400whp. the shop is expecting a 35shot (which is really 70 shot since dual intakes mean two 35shots will spray at the same time) to put out more than 70hp due to the mods i have and the air density. any thoughts there?

4) i have searched and searched on this forum for aftermarket exhaust compared to the nismo exhaust. i cannot find any dyno numbers supporting a change from nismo to aftermarket, only base model to aftermarket. part of the nismo package was supposed to be the better exhaust. swapping to the nismo R tune at this point i think would net maybe another 11-15 hp but its about the same cost as a nitrous kit...could the stock nismo exhaust be a large restrictive factor?


i almost sold my car after i got the dyno numbers back. forced induction does not have the same issues since it compresses the air. i came from the southeast where it was flat so i did not even consider the elevation when i started planning my build. big mistake.

i can provide the dyno sheet, i will have to pull some data logs this weekend as well. any advice here would be much appreciated.

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'14 PW Nismo
Z1 CAI, Z1 HFC, Z1 Ported Upper and Lower Intake Manifold
DC Sports Stainless Headers, JWT C1 Cams, UpRev Tuned

Rusty

Couple of questions.

Who is doing the tuning?

Did you change the rest of the exhaust system, or just the headers, and high flow cats?

Do you have an oil cooler? High oil temps will pull timing. It starts around 240F.

What was the temp and humidity that day?

The Nismo oem exhaust isn't much better than the base exhaust. Only a little louder. The Nismo R Tune isn't much better either.

The DC headers are shorty headers. So don't expect much torque with them. LTH's are the way to go. Either FI or PPE. Followed by the Z1 shorty headers. You're the first person on here to run the DC headers.

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浪人 - 殺し屋
"The Difficult Anytime, The Impossible By Appointment Only"
http://www.the370z.com/members-370z-...o-journal.html

krazynismo

the tuning is done by a shop called turbolab in Orem, UT. they were one of the few shops around here that had experience tuning nissans.

at the time of the tune i had headers, highflow cats, and topspeed axle back non res pipes. everything from the high flow cat (h pipe and mid pipe) to the axle back are stock.

i do not have an aftermarket oil cooler - but even with spirited driving i rarely get above 220ish degrees assuming the factory gauge is somewhat accurate. AFR was between 12 and 13 from 3500RPM up to 7400RPM. max hp was at 7400RPM and AFR was 12.41

i am not sure of the temp or humidity but i will ask the shop. for what its worth there is almost 0 humidity in salt lake city, especially compared to coming from the south east. i would say average temp was probably 90degree F.

i would have rather had the z1 headers but they were on backorder until august. unfortunately due to emissions requirements i am unable to pass the visual inspection with long tube headers. i turned off post cat o2 sensors to keep the check engine light off and can pass visual inspect with the high flow cats.

thank you for your help.

__________________
'14 PW Nismo
Z1 CAI, Z1 HFC, Z1 Ported Upper and Lower Intake Manifold
DC Sports Stainless Headers, JWT C1 Cams, UpRev Tuned

Jhill

An NA car is always going to suffer more at elevation that’s just the way it is. You try running a mile at elevation and see how easy it is once your gasping for air. As for e85 vs 93 you’ll see bigger gains vs 91 than vs 93 but again at elevation I’m not too sure if it’ll be worth it since it’s the lack of air that’s your issue. At the end of the day I think you won’t be happy until your boosted so at least your exhaust is ready for it now.

JARblue

Doesn't sound too far off to me. The Z is pretty efficient NA. You'll have to spend a lot of money to get anything remotely noticeable in terms of power increase. I'm well over $10K in mods with about 10% hp increase from stock

Also, why do numbers even matter? How does the car drive? Do you enjoy it?

If the answer is no, you should sell it and get another car that fulfills your needs. Let someone else who might actually appreciate your car enjoy it

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krazynismo

ill grab a dual nozzle wet shot nitrous kit pretty soon and post some more numbers. its about the same price as an aftermarket cat back (nitrous kit is a little less) and will have much more gains.

i took the non res axle back mufflers off and went back to the super heavy stock nismo muffler - car is a little louder than stock but not much. anyone who asks in person i will tell them the car is stock

for anyone else thinking about building NA 370Z at high altitude i would encourage you to go boosted or nitrous first. ive had several turbo cars and am working on a trailblazer SS with LSA supercharger right now so id like to keep this mostly motor

__________________
'14 PW Nismo
Z1 CAI, Z1 HFC, Z1 Ported Upper and Lower Intake Manifold
DC Sports Stainless Headers, JWT C1 Cams, UpRev Tuned

krazynismo

i really like the 370z - i love the looks and the way it drives. the two tone nismo in white in my opinion is one of the best stock looking cars of the times. it seems every car company started using red accent stripes after the nismo!

i have some friends with some modded cars - mostly 4 cylinder turbos, but the occasional V8. i want to be quick enough to run with them is the reason for upgrading. cruising thru the canyons there is no need for more than 305whp for sure.

__________________
'14 PW Nismo
Z1 CAI, Z1 HFC, Z1 Ported Upper and Lower Intake Manifold
DC Sports Stainless Headers, JWT C1 Cams, UpRev Tuned

SonicVQ

When you post the dyno sheet, we can see what your HP/Torq is corrected for elevation (pressure), temp and humidity.

Most dynos use the "STD" correction factor which adjust the conditions to sea level, dry air (0% humidity) and 60F. That's why most correction factors are almost always above 1.

Your dyno operator might of given you the RAW / actual numbers...

krazynismo

i should have attached the dyno sheet file to this message. SAE correction factor shows as 5.

Attached Images

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__________________
'14 PW Nismo
Z1 CAI, Z1 HFC, Z1 Ported Upper and Lower Intake Manifold
DC Sports Stainless Headers, JWT C1 Cams, UpRev Tuned

SonicVQ

The dyno sheet doesn't show a correction factor number... It only says the correction factor (CF) is SAE, and that the graph "smoothing" is 5.

Here is the problem.... there are two correction standards for SAE:
SAE J607 and SAE J1349.

Generally the J607 (aka STD) is about 4-5% higher than the J1349 standard.
This is due to it factoring in about a 15% loss due to friction.

The dyno results are just numbers on paper. It is very difficult to get accurate and repeatable chassis dyno numbers and on top of this, each engine is a little different.


If the car feels better after the mods, then all is good

If you can post the logs, I will have a look at them... I am curious how the elevation changes things.

Rusty

Your before numbers are on pare for a stock Nismo.

__________________

浪人 - 殺し屋
"The Difficult Anytime, The Impossible By Appointment Only"
http://www.the370z.com/members-370z-...o-journal.html

krazynismo

ahh I misunderstood when I originally replied so I edited my post. sorry for any confusion. really appreciate all the replies here thank you guys

__________________
'14 PW Nismo
Z1 CAI, Z1 HFC, Z1 Ported Upper and Lower Intake Manifold
DC Sports Stainless Headers, JWT C1 Cams, UpRev Tuned

BettyZ

This was my main (stated) justification for going FI. Z didn't have the zip up at 10, 12k feet. That's with full bolt ons, oil cooler, and a tune by Seb.

Sent from my SM-G955U using Tapatalk

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'14 MB Nismo | Boost Lab 6870 1.32 AR 553 HP / 471 ft.-lbs.
Betty Mods

2011 Nismo#91

I don't see those numbers as bad. I was putting similar numbers down for years (NA with bolt-ons and a modest tune) and the car was a blast to drive on the track and ad no issues keeping up with most cars. A dyno sheet is just a piece of paper you can hang some where, having a Corvette racing driver come up to me at Watkins glen and say "Your Nissan's Fucken Fast" is something I will remember for a long time.

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GTR TT 493Whp/431lbft, Ecutek, Southbend 6puck,Quaife, RPM RollBar 4Point, R888R, JRZ RSPro F(10R/10C) R(10R/6C) 1000f500r inlbs+150inlbs Tender, SPL everywhere.Full Specs