Need More Down Low For The Track.

[djr81]

He said hp, not kw

He said KW, not HP

I know what he said - I was trying to agree with the 4000rpm mark.

I havent seen a -5 & and 260 degree cam option on 98 make 300kW at the wheels at 4000rpm. 200rwhp is usually closer to the mark. Broadly I reckon the 200rwhp mark is a measure of decent response as long as you make good (450+rwhp) at the top end.

Other people will doubtless see things differently.

[GTScotT]

I agree here. 200kw @ 4000 is an RB25 based virtue. Thats a motor with a single turbo, VCT to boot and a rev limit of 7000 with the cams to match. So an RB26 which revs to 8 and has two turbos isn't doing bad at 150kw (200hp) by 4000, when at 350kw capable sort of level.

200kw should be do able but would be indicative of a motor with great response (its hit the threshold BEFORE 4000).

So if OP sports 200whp @ 4000 I would say hes not doing too bad, smaller cams might help the ramp pre 4k, but possibly not as phenomenal as hoped. If has 200kw @ 4k then I don't think the setup is doing anything wrong. Should probably try to get the car going faster through corners (as noted by others) or raise the said RPM:speed ratio by moving to 4.3:1 diffs (also said by others).

[djr81]

I agree here. 200kw @ 4000 is an RB25 based virtue. Thats a motor with a single turbo, VCT to boot and a rev limit of 7000 with the cams to match. So an RB26 which revs to 8 and has two turbos isn't doing bad at 150kw (200hp) by 4000, when at 350kw capable sort of level.

200kw should be do able but would be indicative of a motor with great response (its hit the threshold BEFORE 4000).

So if OP sports 200whp @ 4000 I would say hes not doing too bad, smaller cams might help the ramp pre 4k, but possibly not as phenomenal as hoped. If has 200kw @ 4k then I don't think the setup is doing anything wrong. Should probably try to get the car going faster through corners (as noted by others) or raise the said RPM:speed ratio by moving to 4.3:1 diffs (also said by others).

Well he hasnt posted a dyno plot but I would seriously doubt he would see even 150rwhp at 4000rpm with 272 cams.

Here is the difference between Poncam B's and a 256/252 (ie 4 degrees smaller than a Poncam A on the inlet side but with a little more lift). On 98 with -5's. Needs more boost and powers at the top end but the steepness of the curve around 4000rpm demonstrates why a relatively small cam change can make a big hp gain/loss when the thing is coming on boost and why getting the turbros to spool up in the first place is so important.

And no I am not saying there is anything good about the setup on the graph.

As for the cornering speed thing it is really, really hard to gain engine rpm by cornering quicker. Changing the way you drive to a slow in/fast out is the way a GTR needs to be driven anyway.

[RobertPaulson]

What if you're at 4000 in second... Not quite enough on a massive cammed 2.6 with 5's to really get a wriggle on.... You're not gonna go back to first are you?

If you're at 4000rpm in second then you should be on boost and response won't be a problem.

[r32-25t]

Not quite

[RobertPaulson]

Not quite

Sorry for the late reply.

What do you mean? I've done plenty of -5 setups with cams on stock stroke GTR's and they make a bar of boost at 4k if your tuner knows what he/she is doing

[XGTRX]

Sorry for the late reply.

What do you mean? I've done plenty of -5 setups with cams on stock stroke GTR's and they make a bar of boost at 4k if your tuner knows what he/she is doing

Agreed

By 4K they are definitely on song if the cams are advanced enough

[r32-25t]

Why is it the ls1 boys can work out bigger duration cam means the power curve moves up in the rev range but we can't, hell my dad and his mates worked it out in the 70s with their ford and holden v8s.

Hate to tell you but the 30 years between the hq and the r32 Gtr, the physics of the combustion engine didnt change. But for some reason we all seem too ignorant to believe so

[r32-25t]

But to answer the question of more low down torque is more capacity, raise compression, smaller turbos or cam gears adjusted correctly

[zebra]

They would've also figured out that monster cams without matching head work makes you go backwards. Turbos just mask the effect more than an aspirated engine

[XGTRX]

Why is it the ls1 boys can work out bigger duration cam means the power curve moves up in the rev range but we can't, hell my dad and his mates worked it out in the 70s with their ford and holden v8s.

Hate to tell you but the 30 years between the hq and the r32 Gtr, the physics of the combustion engine didnt change. But for some reason we all seem too ignorant to believe so

The difference being is they are NA motors high compression with more than double the capacity but you put big cams in them and they WILL lose bottom end be a pig to drive and struggle to make 300wkw, force air down their throat and its a different ball game. But they can only rev to 6800 safely

A 26 has -5s and cams and has been tuned for mid range....at 4k it is in its sweet spot and ramps all the way to 7500- 8000 safely. rbs need to be revved for the low capaciy low compression engine to make the most of -5s. and get pretty close to 380wkw, much nicer to drive than a cammed v8.

[zebra]

OMFG why do people think V8s cant rev?!?!?!

if a big capacity engine looses bottom end with a large cam, why do you think a low comp small engine wont.

You are dreaming if you think that is the case

In the 60s near standard big blocks would turn 7000rpm+

[Piggaz]

Wanna show me a 2.6, -5's and cams where it's "sweet spot" is 4000 rpm?

[zebra]

By sweet spot I think he means the boost gauge is starting to show positive pressure

[MBS206]

The difference being is they are NA motors high compression with more than double the capacity but you put big cams in them and they WILL lose bottom end be a pig to drive and struggle to make 300wkw, force air down their throat and its a different ball game. But they can only rev to 6800 safely

A 26 has -5s and cams and has been tuned for mid range....at 4k it is in its sweet spot and ramps all the way to 7500- 8000 safely. rbs need to be revved for the low capaciy low compression engine to make the most of -5s. and get pretty close to 380wkw, much nicer to drive than a cammed v8.

Car at 6000 RPM making 300KW is making more torque than youre RB26 that's pushing 380KW at 8000RPM...

Don't need to rev an engine to 8000RPM if it's making more torque down low... It's all about area under the curve... In power band at 2000RPM and revving to 7000RPM is plenty for me... That's a 5K power band... You example only has a 3.5 to 4K power band... And you need to wind it up a bit before you reach it...

[XGTRX]

Big cammed v8 idols at 2000rpm just to keep it alive and usually has a 4-5k stall converter in it and still is a pig to drive. Yes a correctly tuned rb26 with -5s is on song at about 4k and ramps up quickly.

[XKLABA]

4k is to late, the stock cammed stock turbo GTR make 250awkw your chasing around the track has hit boost out of the corner and is half way down the straight while your waiting for boost to come on and when it does he is already on the brakes for the next corner

use a lower gear you say, ok while your fighting the car for traction and changing gear mid corner the stock GTR has put the power down in the right gear for that corner and is nearly at the next one

an rb26 reving to 8-8.5k on the track isn't gonna last long no matter what you've done to it, even the Winfield cars where limited to 7000rpm

[MBS206]

Big cammed v8 idols at 2000rpm just to keep it alive and usually has a 4-5k stall converter in it and still is a pig to drive. Yes a correctly tuned rb26 with -5s is on song at about 4k and ramps up quickly.

So now we're talking automatic drag cars are we?

Old school carby fed V8s will idea high yes. New EFI ones with big cams will nearly idle back at standard idle. Obviously you're showing your severe lack of knowledge here on all things IC related.

[zebra]

Big cammed v8 idols at 2000rpm just to keep it alive and usually has a 4-5k stall converter in it and still is a pig to drive. Yes a correctly tuned rb26 with -5s is on song at about 4k and ramps up quickly.

No...Pro stock 360 cuber making 900+hp will idle at 2000rpm

[XGTRX]

4k is to late, the stock cammed stock turbo GTR make 250awkw your chasing around the track has hit boost out of the corner and is half way down the straight while your waiting for boost to come on and when it does he is already on the brakes for the next corner

use a lower gear you say, ok while your fighting the car for traction and changing gear mid corner the stock GTR has put the power down in the right gear for that corner and is nearly at the next one

an rb26 reving to 8-8.5k on the track isn't gonna last long no matter what you've done to it, even the Winfield cars where limited to 7000rpm

You guys talk as if it takes 5 mins for -5s to spool up well it doesnt, and for those 2 corners on a track where this scenario happens your right but for the the rest of the track a stock gtr will get slaughtered everything else being equal.

About the revving i was just saying, but change gears at 7k and -5 will still be on song.

Changing gears at 8k is not the issue, its when you hold it there around corners things go pop.

I think the Group A cars were limited to 7k as part of the regulations to give the V8s a chance....correct me if I am wrong.

So now we're talking automatic drag cars are we?

Old school carby fed V8s will idea high yes. New EFI ones with big cams will nearly idle back at standard idle. Obviously you're showing your severe lack of knowledge here on all things IC related.

r32-25t was talking about 70s car of which I did have and i stand by what i said. EFI cars are better but a cammed LS1 manual is still a pig to drive and you still have to rev it well above 2k to get it off the line smoothly and stalled autos have a minimum of a 3500rpm stall. So my point is don't even talk about torque under 3-3.5k because a cammed v8 will never be there unless the converter is slipping, and a manual is still surging at 2.5k

No...Pro stock 360 cuber making 900+hp will idle at 2000rpm

ha ha I was exaggerating sorry. But my carby HJ with a pretty aggressive 350 chev wasn't far off