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Discussion Starter #1
Would it be right to that a bolt-on *such as, say... a cold air intake* adds horsepower not by actual HP figures, but by percentage? I came across thisi conclusion when I noticed that SR20s react FAR better to mods than B16s. A cold air intake on an SR20 might add say 8hp or so, and a similar setup on a B16 might only tack on 3hp.

Instead of saying: my intake gives me +10hp, I'm starting to think it'd be more accurate to say: my intake adds + 2% hp or something like that. I think that'd be fitting because larger displacement engines such as the VQs or 2JZs get HUGE gains off what would be considered only a slight increase in a smaller motor. Also, this would make sense because turbo engines get much greater gains off each upgrade.

An SR20DET for example, might get like a 30hp increase (+ 5% hp or something) with an upgraded exhaust, while an SR20DE would only get a 6hp increase (still + 5% hp increase, but the a turbo would make magnify each mods effect) *example only, I'm not sure about actual figures*
 

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FF Drifter said:
Would it be right to that a bolt-on *such as, say... a cold air intake* adds horsepower not by actual HP figures, but by percentage?
No. It has more to do with the compromises and things that could use improvement in the original design.
 

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Discussion Starter #3
So it would be more correct to say than a bolt-on actually tacks on extra HPs...example: a JWT POP will always tack on +10hp, no matter what mods were on the car before. *is that right?*

I was under the impression that a bolt-on would tack on a certain percentage of a car; sort of like a multiplier? In that case; a JWT POP would tack on +10hp on an SR20DE with no other mods, but would add +13hp on an SR20DE that also had S3 cams or something.

By all means, correct me if I'm wrong. ;)
 

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I would say each mod would react to each other as well. For example, if you get ONLY a cat-back echaust and get 5 hp. and No Cat-back exhaust and ONLY header and get 5 hp, if you do the 2 together you might get 12hp since you free up the exhaust system.

It is also important how Good(or how bad, restrictive,) the original design was as GEO said.
 

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FF Drifter said:
Would it be right to that a bolt-on *such as, say... a cold air intake* adds horsepower not by actual HP figures, but by percentage? I came across thisi conclusion when I noticed that SR20s react FAR better to mods than B16s. A cold air intake on an SR20 might add say 8hp or so, and a similar setup on a B16 might only tack on 3hp.

Instead of saying: my intake gives me +10hp, I'm starting to think it'd be more accurate to say: my intake adds + 2% hp or something like that. I think that'd be fitting because larger displacement engines such as the VQs or 2JZs get HUGE gains off what would be considered only a slight increase in a smaller motor. Also, this would make sense because turbo engines get much greater gains off each upgrade.

An SR20DET for example, might get like a 30hp increase (+ 5% hp or something) with an upgraded exhaust, while an SR20DE would only get a 6hp increase (still + 5% hp increase, but the a turbo would make magnify each mods effect) *example only, I'm not sure about actual figures*
I agree with what you're saying, but I'm not sure what you mean by percentage. A percentage of the stock hp?
 

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FF Drifter said:
So it would be more correct to say than a bolt-on actually tacks on extra HPs...example: a JWT POP will always tack on +10hp, no matter what mods were on the car before. *is that right?*
No. No mod will always give the same hp. It depends on too many other factors, including other mods.

FF Drifter said:
I was under the impression that a bolt-on would tack on a certain percentage of a car; sort of like a multiplier? In that case; a JWT POP would tack on +10hp on an SR20DE with no other mods, but would add +13hp on an SR20DE that also had S3 cams or something.

By all means, correct me if I'm wrong. ;)
More likely a mod will add less power if you already have other mods.
 

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Discussion Starter #7
Ahh okay. And what about internal engine mods, like porting and polishing? Do these give greater gains than bolt-ons, or about the same?
 

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FF Drifter said:
Ahh okay. And what about internal engine mods, like porting and polishing? Do these give greater gains than bolt-ons, or about the same?

Once again, it depends upon what you are starting with. I would also say it depends a great deal upon how much hp you are making to start as well.

A P&P will help a NA engine some for sure. It would likely help a turbo engine a lot.
 

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Another thing to add here to maybe help out is that all mods don't help at the same part of the power band. So you may gain 5hp from your exhuast, but it'll be at the top of the rpm band, where a header might help at mid rpms. The peak gain from the header would be somewhere different from the peak gain from the exhuast. So where your exhuast gained you 5hp, your header might only give you an additional 3hp there, instead of the 8-12 peak hp it gives somewhere else in the powerband. And in return the exhuast might only add 1hp where the header peaks. If this makes sense?
 

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Discussion Starter #10
Yeah, I see what you mean. When comparing dyno charts between stock vs. a bolt-on of some kind, the graphs would peak at different points and such like that. Is that about right?
 

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FF Drifter said:
Yeah, I see what you mean. When comparing dyno charts between stock vs. a bolt-on of some kind, the graphs would peak at different points and such like that. Is that about right?

Uhh... not really peak at different points, peak still says pretty much the same unless you throw in different cams, that's what'll move it around a lot. The other stuff just adds more area under the curve in different places. For example, from 4K-5K you might notice a higher hp figure than stock if you add a header (more area under the curve) but your peak may still remain at ~6400rpms.
I'd think that most people's goal with mods is to add as much area under the curve as possible for a quick street car. When you start racing competitively it changes everything. =)
 

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JustinP10 said:
Another thing to add here to maybe help out is that all mods don't help at the same part of the power band...
By the same token. It would seem to me that the highly-touted ignition advance mod would only be effective at higher revs. Please correct me if I've got this wrong.
 

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Gaz said:


By the same token. It would seem to me that the highly-touted ignition advance mod would only be effective at higher revs. Please correct me if I've got this wrong.
Dyno proven, mother approved. ;) Advanced timing helps the entire power band. Approx 2-5hp throughout the band. It's so linear that's it's hardly noticable.
 

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Discussion Starter #14
So it just bumps the entire curve up about two to five notches?
 

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Geo said:
More likely a mod will add less power if you already have other mods.
could you explain this a little more. do you mean that a header w/ claimed 10-12hp will only gain say 7hp w/ other mods like intake. or do mods contradict themselves like if i have an intake and get headers my 3-5hp from intake and 10-12hp from header will only add to 9-11hp. or am i totally wrong on all of this.
 

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greekman said:


could you explain this a little more. do you mean that a header w/ claimed 10-12hp will only gain say 7hp w/ other mods like intake. or do mods contradict themselves like if i have an intake and get headers my 3-5hp from intake and 10-12hp from header will only add to 9-11hp. or am i totally wrong on all of this.

Sorry for the confusion. Good question.

What I meant was exactly what you first wrote.... Adding a mod that is known to add 10 hp might not add that depending upon other mods.

Also, Justin is quite correct that a mod may be known to add a certain amount of hp, but it may not be peak hp.
 

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thanks. i thought it was the first one, but i didn't know for sure.

could you (geo) or someone give a breakdown as to where in the powerband mods peak at. for instance:
header-12hp peak at 6500rpm
intake-4hp peak at 4000rpm
etc...
 
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