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Moving peak power - cams

Gts-t

By Gts-t,
in Engines & Forced Induction

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Gts-t Grand Master

Gts-t

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Posted

Hey all,

currently i am running a hks2530 on my rb20 and making peak power around 6000rpm. I would like to make peak power closer to 7500rpm without changing the turbo. I understand the cams are causing this. It shits me because i want to use the extra 1500 rpm! i may as well have a sr20, jks, they are way to lame.

My question is what cams from hks or tomei would do this? I am not looking to increase the power hugely as the extra 1500 rmps in the power = torque x revs equasion should be enough to inrease it perhaps a little. I think the turbo will become the restriction at those revs then maybe...?

Anyones experience with step one style cams(not GTR) in a rb20 would be much appreciated.

Changes at 6000 are ok, but changes at 7000-7500 would be more fun

:D

PS. a RB30det(t!) seems like a better option the more i think about it as the internals could remain stock and make some pretty bullshit power, but then i wouldnt be changing at 7500 rpm either, spose id be going fast atleast...

*scratches head some more*

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Gts-t Grand Master

Gts-t

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how come your changing  gears at peak power instead of past peak power?

usually u go a bit past peak power before you change gear, ie if its making it a 6, id probably be changing around 7 anyway

I would consider that sloppy, the car is losing power, better to change gears. Others?

Gts-t Grand Master

Gts-t

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Even If its losing power you still revv a rb20 out till atleast 7500 so u can drop it back into its torque range again once u change gears. The tomei poncams 260 degree are sweet as on rb20. Even the 252's stop power dropiing off.

You dont if its only running a smallish turbo (HKS2530) and i think the major drop in revs is only from 1st to second. Roy and a few others could refresh my memory there.

lang Collaborator

lang

Posted
Posted
I would consider that sloppy, the car is losing power, better to change gears. Others?

well, you want to change gears slightly past peak power, to get the most out of it, the power is a curve, so it peaks and then tapers off. It is best to change slightly into the taper, so when you change into the next gear, the engine will be closer to the RPM peak power is made than if you had changed right at peak power.

obviously it depends on how fast it drops off, as to when you should change, and also to an extent where the torque curve lies. thats something you have to judge as the driver.

NickR33 Grand Master

NickR33

Posted
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yeah its something you have to worry more about in na cars, you may as well just pull the next gear in a turbo and use the torque, as long as your still at full boost and your not granny shifting... I read an interview with fred gibson on this topic and he believed there wasn't much point in revving the guts out of a turbo, better to just grab the next gear...

Gts-t Grand Master

Gts-t

Posted
  • Author
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well, you want to change gears slightly past peak power, to get the most out of it, the power is a curve, so it peaks and then tapers off. It is best to change slightly into the taper, so when you change into the next gear, the engine will be closer to the RPM peak power is made than if you had changed right at peak power.  

obviously it depends on how fast it drops off, as to when you should change, and also to an extent where the torque curve lies. thats something you have to judge as the driver.

Ok mate thanks, i know that and yes you are right slightly over.

However 6000 is already slightly over and i want to change at slightly over 7000 rpm. Then what. I need answers to my question not a debate on how far after peak power to change gears. thanks for the help though

That 6000 already took into account slightly over. Peak power is made at 5750 drops 10hp by 6000 then 20 by 6250. So anything over a 6000 change im considering as sloppy etc.

Would really like to take advantage of the extra 1500 or so rmp that are available if i can do so without changin the HKS2530 turbo..

Mick

Gts-t Grand Master

Gts-t

Posted
  • Author
Posted
yeah its something you have to worry more about in na cars, you may as well just pull the next gear in a turbo and use the torque, as long as your still at full boost and your not granny shifting... I read an interview with fred gibson on this topic and he believed there wasn't much point in revving the guts out of a turbo, better to just grab the next gear...

Thanks for stating the obvious i love it. Can you guys leave the posting to people like SK and luke vl, poeple who actually know a thing or two about cam timing and profiles etc.

The last thing i need is tips on when to change gears.

Sydneykid Grand Master

Sydneykid

Posted
Posted
Hey all,  

currently i am running a hks2530 on my rb20 and making peak power around 6000rpm. I would like to make peak power closer to 7500rpm without changing the turbo. I understand the cams are causing this. It shits me because i want to use the extra 1500 rpm! i may as well have a sr20, jks, they are way to lame.

My question is what cams from hks or tomei would do this? I am not looking to increase the power hugely as the extra 1500 rmps in the power = torque x revs equasion should be enough to inrease it perhaps a little. I think the turbo will become the restriction at those revs then maybe...?  

Anyones experience with step one style cams(not GTR) in a rb20 would be much appreciated.

Changes at 6000 are ok, but changes at 7000-7500 would be more fun

:D

PS. a  RB30det(t!) seems like a better option the more i think about it as the internals could remain stock and make some pretty bullshit power, but then i wouldnt be changing at 7500 rpm either, spose id be going fast atleast...

*scratches head some more*

Well .......... cams may not help, you may be maxing out the airflow of the 2530 at the boost that you are running. Also the efficiency of the other components (inlet, intercooler, dump, exhaust etc) and/or tuning may be the issue, not the cams. Post up the power graph with boost and A/F ratio traces and I might be able to help some more.

My reasoning is due to the fact that our old RB20DET made good power to 8,250 rpm with the standard cams. It's all airflow related and cams weren't the weakest link.

:)

Gts-t Grand Master

Gts-t

Posted
  • Author
Posted
Well .......... cams may not help, you may be maxing out the airflow of the 2530 at the boost that you are running.  Also the efficiency of the other components (inlet, intercooler, dump, exhaust etc) and/or tuning may be the issue, not the cams.  Post up the power graph with boost and A/F ratio traces and I might be able to help some more.

My reasoning is due to the fact that our old RB20DET made good power to 8,250 rpm with the standard cams.  It's all airflow related and cams weren't the weakest link.

:D

Thanks SK, i figured i would max the turbo out that why i was wondering if i could just move the peak pwer point higher and keep the power about the same. The aim would be to make the power stay the same from 6000 rpm to 7500 rpm. If there is any point to this i dont know. Seems like im digging myself a hole on this one as the extra rpm would certainly increase power too much at the same boost level.. /rambling

FWIW i have the same set up as bbenny and only have his dyno grahp to go off right now, my dyno does not print graphs. I will be pushing teh standard MAF and inj to there limit as the turbo like you say will run out of puff just above that.

Thanks for the advice SK i will stick with the standard cams and start looking for a rb26 head for a rb30dett conversion. and dont worry ill keep you updated (with questions)

Mick :)

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