Maintaining torque at higher rpm in a Mk 2?
Discussion
I have a Mk 2 (1999) 10th Anniversary with racing beat manifold and roadstersport back box. This car also has the more aggressive BP5A "Mazsaspeed" inlet cam as standard.
Flooring the accelerator at around 3,000 rpm gives a surge in torque which promises big things, only for the torque to drop off from there to the redline.
What I'd like to know is how to better maintain this initial surge in torque higher up the rev band.
The car has the original midpipe and cat fitted with 120K miles on it, would decatting this and/or upping the pipe diameter to 2.25" help, or is it a waste of time?
Similarly, will using adjustable cam gears move the torque curve higher up the rev band, or do I really need aftermarket cams and headwork to keep the torque higher up?
Would modifying/gasflowing the head on its own be of benefit, I understand that this can be done for as little as a three hundred quid with documented flow characteristics?
Flooring the accelerator at around 3,000 rpm gives a surge in torque which promises big things, only for the torque to drop off from there to the redline.
What I'd like to know is how to better maintain this initial surge in torque higher up the rev band.
The car has the original midpipe and cat fitted with 120K miles on it, would decatting this and/or upping the pipe diameter to 2.25" help, or is it a waste of time?
Similarly, will using adjustable cam gears move the torque curve higher up the rev band, or do I really need aftermarket cams and headwork to keep the torque higher up?
Would modifying/gasflowing the head on its own be of benefit, I understand that this can be done for as little as a three hundred quid with documented flow characteristics?
Edited by youngsyr on Wednesday 16th June 21:23
Do you have a dyno graph plot for the engine in its current state of tune?
While other factors have an effect. The torque profile is largely dictated by the cam(s) profile.
Multivalve cylinder heads (usually DOHC) allow more aggressive cams to be run and with higher rpm ranges. Clever tech like VTEC, VCT, VVC and variable length inlets all promote making use of the upper rpms.
I can't talk specifics for the MX-5, so this is only general info and a rule of thumb, although it should still apply.
This is a Focus ST170.
Note how it makes good torque from as low as 2500 all the way to well over 6000rpm. But from it's PEAK at around 5000rpm it starts to nose off. So would feel as though it isn't accelerating at the same rate. If you fitted a more aggressive cam, it would essentially move this curve to the right. So would appear to make less torque at 2500rpm, it's PEAK would be higher in the rpms and it'd nose off earlier.
Compare this to a Civic Type R. You can clearly see where the VTEC engages, which essentially is a more aggressive cam profile. The torque increases, and because:
HP = torque x rpm/5252
You get more power with more torque, even at the same rpms. This is what makes the VTEC feel so revvy and willing at high rpms.
As I said, I can't comment for the MX-5 directly. But a dyno plot would show what your car is currently making and the curve profile.
If however it is a very noticeable drop off in power at higher rpms, then it may be some other form of issue. Poor fuel or spark delivery may cause this, as would a mis-timed cam or some sort of tuning issue due to the current mods.
Hope this helps, although based on your other replies to me, I'm sure it won't....
While other factors have an effect. The torque profile is largely dictated by the cam(s) profile.
Multivalve cylinder heads (usually DOHC) allow more aggressive cams to be run and with higher rpm ranges. Clever tech like VTEC, VCT, VVC and variable length inlets all promote making use of the upper rpms.
I can't talk specifics for the MX-5, so this is only general info and a rule of thumb, although it should still apply.
This is a Focus ST170.
Note how it makes good torque from as low as 2500 all the way to well over 6000rpm. But from it's PEAK at around 5000rpm it starts to nose off. So would feel as though it isn't accelerating at the same rate. If you fitted a more aggressive cam, it would essentially move this curve to the right. So would appear to make less torque at 2500rpm, it's PEAK would be higher in the rpms and it'd nose off earlier.
Compare this to a Civic Type R. You can clearly see where the VTEC engages, which essentially is a more aggressive cam profile. The torque increases, and because:
HP = torque x rpm/5252
You get more power with more torque, even at the same rpms. This is what makes the VTEC feel so revvy and willing at high rpms.
As I said, I can't comment for the MX-5 directly. But a dyno plot would show what your car is currently making and the curve profile.
If however it is a very noticeable drop off in power at higher rpms, then it may be some other form of issue. Poor fuel or spark delivery may cause this, as would a mis-timed cam or some sort of tuning issue due to the current mods.
Hope this helps, although based on your other replies to me, I'm sure it won't....
Edited by 300bhp/ton on Wednesday 14th July 15:22
youngsyr said:
The car has the original midpipe and cat fitted with 120K miles on it, would decatting this and/or upping the pipe diameter to 2.25" help, or is it a waste of time?
Similarly, will using adjustable cam gears move the torque curve higher up the rev band, or do I really need aftermarket cams and headwork to keep the torque higher up?
Would modifying/gasflowing the head on its own be of benefit, I understand that this can be done for as little as a three hundred quid with documented flow characteristics?
Similarly, will using adjustable cam gears move the torque curve higher up the rev band, or do I really need aftermarket cams and headwork to keep the torque higher up?
Would modifying/gasflowing the head on its own be of benefit, I understand that this can be done for as little as a three hundred quid with documented flow characteristics?
300bhp/ton said:
I can't talk specifics for the MX-5, so this is only general info and a rule of thumb, although it should still apply.
300bhp/ton said:
This is a Focus ST170.
300bhp/ton said:
Compare this to a Civic Type R
300bhp/ton said:
Hope this helps, although based on your other replies to me, I'm sure it won't....
It's about as helpful as all of your other posts on here.Perhaps I should append a "Please stay on topic and refraing from posting vague ramblings about completely unrelated topics/cars/issues that do nothing to answer my specific question" advisory to my posts. I bet even then it wouldn't help.
Edited by youngsyr on Wednesday 14th July 15:45
Or maybe I should reply "don't be such a cock" when people are trying to help you.
If you car runs fine, but you don't like the performance, it'll be the cam profiles combined with a small displacement n/a engine. But since you didn't post any specs on them or a dyno plot its nigh on impossible to tell. And without diagnosing the issue (if one exists), then any solution is pure false hope.
If it isn't this, then it's likely (although not exclusively) one of the other things I mentioned. Make, model and engine make no odds, all IC petrol piston engines work in roughly the same way.
If you don't like the advice or help. Don't heed it, but why be such a prick about it?
If you car runs fine, but you don't like the performance, it'll be the cam profiles combined with a small displacement n/a engine. But since you didn't post any specs on them or a dyno plot its nigh on impossible to tell. And without diagnosing the issue (if one exists), then any solution is pure false hope.
If it isn't this, then it's likely (although not exclusively) one of the other things I mentioned. Make, model and engine make no odds, all IC petrol piston engines work in roughly the same way.
If you don't like the advice or help. Don't heed it, but why be such a prick about it?
Edited by 300bhp/ton on Wednesday 14th July 15:50
300bhp/ton said:
Or maybe I should reply "don't be such a cock" when people are trying to help you.
If you car runs fine, but you don't like the performance, it'll be the cam profiles combined with a small displacement n/a engine. But since you didn't post any specs on them or a dyno plot its nigh on impossible to tell. And without diagnosing the issue (if one exists), then any solution is pure false hope.
If it isn't this, then it's likely (although not exclusively) one of the other things I mentioned. Make, model and engine make no odds, all IC petrol piston engines work in roughly the same way.
If you don't like the advice or help. Don't heed it, but why be such a prick about it?
On the contrary, this is the MX-5 forum and the reason it has it's own forum is because there are a lot of owners who post on here.If you car runs fine, but you don't like the performance, it'll be the cam profiles combined with a small displacement n/a engine. But since you didn't post any specs on them or a dyno plot its nigh on impossible to tell. And without diagnosing the issue (if one exists), then any solution is pure false hope.
If it isn't this, then it's likely (although not exclusively) one of the other things I mentioned. Make, model and engine make no odds, all IC petrol piston engines work in roughly the same way.
If you don't like the advice or help. Don't heed it, but why be such a prick about it?
Edited by 300bhp/ton on Wednesday 14th July 15:50
For that reason I asked specific questions about my car that I was hoping someone who had already asked those questions, and perhaps answered them on their own car could help.
I didn't ask for a generic lecture from someone who has little to no knowledge about my car about how to increase torque higher up the rev range on completely different cars, or even in general. If I did want that, I'd ask general questions in the General Gassing forum, not specific questions in the MX-5 forum.
As for why I'm being such a prick about it, I believe that you've answered that question by searching for other long-dead posts by me to continue to post your ramblings on after I shot you down on the other thread.
Still, why not take this thread even more off topic than you already have, eh?
Edited by youngsyr on Wednesday 14th July 15:59
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