FI redline changes? 8500RPM?

[NetViper]

With the AEM, the tuner asked me if I wanted to take the redline up to say 8500 with the low-comp motor. I told him to leave it at 8000. I am curious, has anyone with AEM brought it up? Is it safe?

Thoughts? Opinions?

 

[peiserg]

i accidentally (at 90 mph) dropped it from 5th to 2nd in my accord. Revved pretty high and didn't break anything. does that help?:tongue:

 

[Hoover]

Take a look at your dyno chart.
Most FI motors will peak earlier and WOT isn't necessary.

 

[NetViper]

Take a look at your dyno chart.
Most FI motors will peak earlier and WOT isn't necessary.

Not with the BBSC. As the revs climb, so does the HP.

 

[Ojas]

Redline vs. cutoff

With the AEM, the tuner asked me if I wanted to take the redline up to say 8500 with the low-comp motor. I told him to leave it at 8000.

I don't have the answer, but want to make sure we're all talking in the same terminology: On a stock manual transmission NSX, redline is 8000 RPM and fuel-cutoff is 8300 RPM. So you're talking about raising your fuel cutoff 200 RPM over stock.

 

[Hoover]

Not with the BBSC. As the revs climb, so does the HP.

That's because of the specifications of the charger itself. It will make more top end power, but suffer on the lower ends.
As we all know, WOT power band isn't the most useful type of hp., but it's bragging rights.


This will give it a very narrow power band to say the least.
Also, you have to consider the higher piston speeds which can/will/usually equate to short term engine life; especially with FI motors.

For reliabiltiy and overall performance, you want to keep the power band in the middle where it's useable/safer.

 

[Bob Kenney]

I know of some NA engines that are flirting with 9K but theses are all-out race engines and built for the task. Vale float can become a problem at high RPM if the springs are not sufficent to keep the cam followers riding the lobe and it the valves make contact with the piston its LUNCH TIME.

Bob

 

[Hoover]

I know of some NA engines that are flirting with 9K but theses are all-out race engines and built for the task. Vale float can become a problem at high RPM if the springs are not sufficent to keep the cam followers riding the lobe and it the valves make contact with the piston its LUNCH TIME.

Bob

Absolutely!!!

Most N/A "race" motors reduce the piston speeds, by destroking the engines which allows them to run higher RPM's "safer".
A 3.25" stroke @ 8500 rpm will have an average piston speed of 4604 ft. per minute. Destroking to 2.5" stroke @ 8500rpm will give you an average piston speed of 3541 ft. per minute. With a caluclation of 9000rpm we'd still yield a 3750 ft. per minute piston speed, which is fairly safe for the lower end of the engine.

One thing to consider when building a street motor vs. a full race motor, n/a vs. FI motor is the difference in useage of hardware and relavtive materials of the base engine itself. A full race motor probably won't run as well on the street and a street motor may not last a full enduro race.

 

[NetViper]

That's because of the specifications of the charger itself. It will make more top end power, but suffer on the lower ends.
As we all know, WOT power band isn't the most useful type of hp., but it's bragging rights.


This will give it a very narrow power band to say the least.
Also, you have to consider the higher piston speeds which can/will/usually equate to short term engine life; especially with FI motors.

For reliabiltiy and overall performance, you want to keep the power band in the middle where it's useable/safer.

You must be talking about cars other than the NSX because it has a very narrow power band stock. 5500-8000 RPM is the powerband on this car.

Regardless, I am keeping it at 8000 for safety reasons.

 

[Hoover]

You must be talking about cars other than the NSX because it has a very narrow power band stock. 5500-8000 RPM is the powerband on this car.

Regardless, I am keeping it at 8000 for safety reasons.

A "FI" NSX specifically. However, this principle does apply to the "average "street trim FI car.

The power curve on a CTSC begins in the mid 2k range while the BBSC makes it's hp on the upper end.

 

[Larry Bastanza]

The weak link in the NSX engine, in regard to redline, is the oil pump gear set. I would not change the redline unless you have installed the billet gears at least. I would say with your boost levels you should just leave well enough alone.

My $.02.

LarryB

 

[NetViper]

The weak link in the NSX engine, in regard to redline, is the oil pump gear set. I would not change the redline unless you have installed the billet gears at least. I would say with your boost levels you should just leave well enough alone.

My $.02.

LarryB

According to Andy, the motor was rebuilt with Comptech Oil Pump Gears.

I think Wei-shen bumped his redline up to 8500 RPM. That is why I was a little curious.

 

[BryanZublin]

Re: Redline vs. cutoff

On a stock manual transmission NSX, redline is 8000 RPM and fuel-cutoff is 8300 RPM.

Fuel cut is actually at 8000 RPM as measured on my 1992 NSX. The NSX tach reads high (error) at that RPM. I know that the Honda technical book says 8300 RPM but I dispute this based on my measurements.

 

[NsSeX]

If I remember correctly, the turbo charged 1995(?) lemans GT1 NSX had a redline of 8500. Does that help?

 

[len3.8]

Time to start Flying Viper....

 

[coldhammer]

I have my rev limiter set at 8500. So far no problems. But then in all honesty its not very often I go above the 8k mark. I will have to do a search regarding the oil gears though as I am not familiar with that issue.

 

[Yellow Rose]

Hammer - there are many documented cases of the factory oil pump gears failing at extended (as in track events = 8000 RPM, though I personally know of a street failure at about 35 MPH not at redline) engine speed.

Comptech and Dali offer stronger gears.

If just upgrading the gears, it is a rather expensive proposition. However, if the engine is already apart for a re-build.....no-brainer.

If the factory oil gears shatter, there will be ZERO oil pumped to the engine bearings.

Tick tick tick tock tock tock tap tap tap bang bang bang.....you get the picture.

 

[D'Ecosse]

....Most N/A "race" motors reduce the piston speeds, by destroking the engines which allows them to run higher RPM's "safer".
A 3.25" stroke @ 8500 rpm will have an average piston speed of 4604 ft. per minute. Destroking to 2.5" stroke @ 8500rpm will give you an average piston speed of 3541 ft. per minute. ....

Sure - but you also have to take into consideration that the engine displacement is going to be reduced by ~ 25%!
Reducing the stroke from stock 3.5" by same 3/4" on 3.0 NSX would reduce the net displacement to ~ 2350 cc!

But I think you're just explaining the theory here, not suggesting considering actually doing that.

That's why turbo's make so much more sense than superchargers - it's all about the torque, folks! With a flat torque curve there is no need to shift at redline as long as you are in the torque-band (never mind the power band).

Check this out .......


.

 

[NetViper]

Comptech and Dali offer stronger gears. .

Which I do have right Andy?

Regardless, I am keeping the redline at 8000.

 

[winreboot]

I'll soo agree with D'Ecosse. On my turbo setup I never redline, I usually go as high as 7,500, but most of the time I shift much earlier like 6,800 or 7,000 When I'm in my tq power band I have the rear all over the place. Today I change the boost and boosted 23psi @ 4,700rpm's and it was wild :biggrin:
But with supercharger it might be different

 

[Sig]

. Today I change the boost and boosted 23psi @ 4,700rpm's and it was wild :biggrin:
But with supercharger it might be different

23psi, holy sh&*...... I hope that is with a relatively small compressor! What kind of power do you think you're making at that boost level?

At 15psi and above, I'm well above 500 rwhp. At 23psi either my tranny would explode or my axles would fail before I got to 5000rpms.

 

[WOODY]

WHAT??!!!!!??? This must be the most boost ever on an NSX. if 15 psi = 500rwhp you must be at 650? how do you do that with 550 injectors?

 

[Elite]

WHAT??!!!!!??? This must be the most boost ever on an NSX. if 15 psi = 500rwhp you must be at 650? how do you do that with 550 injectors?

If he indeed has 550's, then like suggested above, the turbo is probably pretty small. And not making near the hp #'s you may think. But would definately give him the torque/seat of the pants feel he is talking about.

 

[winreboot]

I'll post my aem log when I get home. I don't have big turbine it is .83 housing t3/t4. I had my engine rebuild with low comp pistons 9:1 after I lost a piston last year. Car pulls like crazy when on boost when over 15psi, but I normally keep it 14psi only yesterday I turn up the boost to see how it runs over 20psi. But I did not push it to redline. I stop at 5k. Last time I dyno it with 14psi I made 420hp and 360tq. Small turbines will make more tq and less less hp, but are more fun to drive. AFR was around 12.07 it is daily driven car

Dave

 

[WOODY]

is your turbo a custom setup?