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who determines the engines redline?


olddragger

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As Jeff has said "I am different".

Hopefully soon I will be getting my car classed. I appreciate everyones help to date. Great group.

This is my situation. I run a supercharged rotary engine (RX8).

My engine builder has told me that 8K is my redline. My car is tuned by an oem ecu flash, and i am unable at this time to have multiple maps.

The stock redline is 9K and it is only a warning buzzer--damn thing would wind out forever i think.

Presently i have no way to reset that warning buzzer. i do have ob2 data collection capacity for every session.

The engine has enough blower and fuel to make additional power between 8-9.5K, but i am not going there. It is also my daily driver and i am not interested in squeezing out another 10 hp only to not have the engine last very long.

Delima---what do i do?

OD

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i didnt either Don, just trying to keep it honest even though i will NOT be a front running car in TTB!

OD

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  • National Staff

This is definitely a problem. Once we are using GPS regularly to test compliance, it won't matter nearly as much. However, if you have a motor that is physically capable of making more power, and their is no actual rev limiter put on it, then how would you propose that we allow you to run based on those lower levels (that are adjusted by your foot)? We do not have the time or manpower to check your OBD2 data recordings after each session you run. As far as I'm concerned, if we have a car that is not rev limited, and the power curve on the Dyno is still heading upward at the point that the owner wants the Dyno operator to stop the testing, we should just extrapolate where that curve is headed to the actual known redline. However, as you state, it is not specifically written in the rules. It is written in the rules that NASA will determine how to run the Dyno testing, though. And, if I am running the testing, and I have this situation, then I will just determine that the owner is failing to be compliant with the testing by not allowing testing to redline--ie, DQ. We unfortunately cannot just rely on the word of a competitor that he won't run past a certain rpm on the track when there is nothing to physically stop him/her, and we do not have the methods/resources available to adequately ensure compliance.

 

As well, I have not seen your request for Dyno re-classing. I'm hoping that you are not under the impression that you can just max the car out at the limit of Adjusted Wt/Hp ratio for a class, and then choose your own base class to start calculating your points at.

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No sir, it's not me, I have a normally aspirated RX-8 with a defined redline. I have no problem pushing it to that point. Denny, the OP, is in the discovery stage of joining in the TT group with an FI'd RX-8 and is asking the questions. I've just been trying to help him get in properly. Your input is much appreciated.

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  • National Staff

Don, sorry, I was referring to the O.P. who has the aftermarket FI, but has not Dyno re-classed yet.

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Greg--thanks for the quick reply.

I concur with all you have said.

As my friend Don posted, i am trying to do the right thing in order to get classified properly, thats all.

I was going to balanced performance (near road Atlanta) in a couple weeks for my dyno sheet and needed to clarify what I needed to do.

Here is a dyno graph from a very similar prepared car

 

http://i297.photobucket.com/albums/mm205/doorcombo/Graph.jpg

 

I expect very similar results from mine.

 

here is one going to 9K (this one has a lower peak hp but you can see the rise in hp as the rpms increase)

http://www.rx8club.com/attachment.php?attachmentid=155808&d=1273018871

 

You would not believe the difference in heat production, etc that 1K produces.

Factory rev limit is 9.5.

e shaft bends at 10.3

aint going anywhere near there for another 10-15hp.

 

At this point i dont know what to do.

I do not have a stand a lone ecu and the factory doesnt have a factory cut even close to 8K.

I do not know on anyone that can lower the rev limit. I dont think the Cobb unit can do that. It can increase it but not lower?

Looks like i am out of luck?

olddragger

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can you not have the tuner tune it so your dyno plateaus at your self imposed RPM rev limit?

or can u limit the boost above certain RPM's?

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hey mate--get those brakes fixed yet? Sorry you are having troubles like that.

I have been networking today about this and it seems the Cobb tuning device can do it --but they are around $400 used. Plus paying someone to do it.

looking bleak.

OD

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If it was turbocharged he could cut back the boost towards the top, not so much with a supercharger. Although I guess you could set up a blow off valve with an electronic boost controller and try to use it like a wastegate. Crazy but it could work.

 

To the OP, what do you use to tune it now if you don't have a Cobb AP? 'OEM ECU flash' doesn't sound like something that could handle changing a n/a car's tune for forced induction.

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The kit has a flash by the builder--Pettit Racing based in Florida.

He has not explored changing the redline warning/cut in the oem software. Some customers of his do not mind going to 9K. They must have deeper pockets than I.

To tell you the truth I dont want to spend $500 to buy a cobb unit and get my redline changed. Thats ridiculous.

What I MAY be able to do is just suck it up and get a dyno to 9K crossing my fingers, just one pull. Then afterward run the car as I intend.

Since I am running water injection I would still have water spraying if a fuel cut occured. Once the fuel came back I dont know what would happen?

Didnt mean to get so complex and confusing guys.

As Jeff England has always told me--I am differant. He started that after I messed up the passengers seat of his vette coming out of turn 5 at rd Atl.

Thanks for all the help---it will get done one way or the other.

OD

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  • Members

What I MAY be able to do is just suck it up and get a dyno to 9K crossing my fingers, just one pull. Then afterward run the car as I intend.

 

 

 

That is precicely what you must do. You have no option in the matter barring a rev limiter to be compliant within the rules. You will need 3 pulls for the dyno reclass and subsequent car classification form.

 

I codrive a TTD RX8 that has had the ECU reflashed. The redline has been moved up to somewhere around 10,000 rpms. I find the car pulls harder by shifting around 8,500rpms and my lap times are pretty consistently 2-3 seconds faster than the owners times. He loves to rev the piss out of it, I dont see any need for it so I drive the car accordingly. Ive had several conversations with Robert Davis on the subject. He suggests that we should never rev past 8700 rpms. Seals dont like it and the motor just doesnt live by reving it out beyond that. FWIW.

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thanks Shawn. couple years ago i was hanging with Roar Racing and Mr Davis's nephrew Billy.Gave him a ride back to the airport in Atlanta. We were speaking of the too high redline set by the factory way back then.

But you are right and thats my plan. "Just dyno the dang thing and get on with it."

Be my luck i will be making too much hp for my weight now!

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thanks Shawn. couple years ago i was hanging with Roar Racing and Mr Davis's nephrew Billy.Gave him a ride back to the airport in Atlanta. We were speaking of the too high redline set by the factory way back then.

But you are right and thats my plan. "Just dyno the dang thing and get on with it."

Be my luck i will be making too much hp for my weight now!

 

 

You might be but at least its honest.

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SOme say that is a fault of mine. I cant help it, my father beat it into me (not literaly).

Dyno last week in July.

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well good news is after exploring deeper i found that the oem limiter uses throttle body positioning. Once at redline it cuts the tb back to 20%.

That makes me feel a little better. I will not have to worry about a lean condition nor over injecting water as that system is triggered by maf voltage.

Appreciate all the help guys. Yall must want me on track so i can wave yall by?

OD

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I thought the best use of the sky-high revs in the rotary was winning bar bets.

"I'll bet you $100 that I can hit 10K RPM and hold it 10 seconds!"

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While it wouldn't be ideal, you could bump up the competition weight a little to account for the slightly higher power the dyno would represent, no? That is referring to staying in TTB, if a class change is in order (and if you will actually be in TTB).

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  • National Staff

From what I saw of his previous posts, based on the power levels and weight, he may not be in TTB anyway. I still have not received a request for Dyno re-classing. We do already have a turbo RX-8 under Dyno re-classing, though, in PTB with what sound like lower HP and higher weight numbers.

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hey guys.

My dyno will occur either next week (work allowing) or the following.

I am almost positive i will be at the 315-325whp range. I do have maf readings of 365grams/sec now (ambiet was at 90F).

I will have around 200 tq is all---remember it is a rotary!

My best guess on wgt will be 3250-3300lbs (racing wgt).

wgt and dyno to be done at Balance performance--close to Road Atlanta. About 110 miles away from me.

Points will be from:

varient 3 coilovers

racing beat sways (front and rear)

hoosier r6 245/35/18

no aero

thats all I know.

I really dont want to add ballast on my DD car, but it all depends.

x fingers--it will be close. sigh

Now yall do know that i am doing this just so yall will have another car to pass!?

just a word...left side passers will get chewing gum thrown their way. I tried tobacco one time but that didnt work too good----forgot I had a full helmet on.

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  • 2 weeks later...

well no TT for me. After dyno and weight i would have to add too much ballast for my dd--dont want to carry that around every day.

Thanks for all ya'lls help.

I will be there in HP3/4--still waving yall by!

OD

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well no TT for me. After dyno and weight i would have to add too much ballast for my dd--dont want to carry that around every day.

Thanks for all ya'lls help.

I will be there in HP3/4--still waving yall by!

OD

 

TT is a lot easier if you start stock and build to the rules instead of bringing a modded car over - Spec Miata, E30 come to mind....

 

See you at the track

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