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Originally Posted by chetanhanda  if the 10% throttle input revved upto Xrpm now it will be (X+n) rpm
it will make more power if the original TB was so restricted that the power was being held back due to the bottleneck.
so if the existing TB is a bottleneck (and also if the OEM manufacturer was a retard) then it would make sense to upsize.
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i guess we do have a few retards around
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A stock engine may have a TB size perfectly port matched for this mass and velocity of air flow,
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Atleast in India, i dont think many cars have ports,TBs and manifolds matched.
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e.g the speed density fuel map has x= MAP reading , y= RPM ,z = duration of Injector pulse , so if the ECU sees more air it simply looks up x2y2z2 instead x1y1z1 so u just getting the stock power (over simplified ) of a higher rpm at a lower rpm
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It cant be stock power of higher RPM at lower RPM ..... For a given condition, with more air its only z and x that changes.....
Either way, i dont think VE will be same in both cases.. Irrespective of throtle position, VE at 30% load with one TB setup may not be same with another TB for same load. The combination of intake sub-systems will have a say on VE .
Its different on MAF systems though.
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what the the MAP will indicate depends on how much air you pull in, its only that the MAP will now indicate higer value for a lower TP angle becoz for this TP angle more air is sucked in becoz of the larger TB size.
(guys plz dont confuse alpha/TP angle with speed density reading this last sentence,speed density= MAP,alpha/Tp angle=TP angle)
none of the cars in iNdia work on alpha-n so dont worry abt this...
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The Ford escorts and if i remember correctly the early versions of opel astra had alpha-N
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more air= MAP sensor indicates greater value = ECU uses a value from the fuel MAP corresponding to that MAP value and more aggrressive pickup (not more power)
but hey the TB maynot be that bad,Im guessing that at WOT maybe you will see the gains becoz there the ECU goes in open loop , its here the extra air may help a bit will it be noticeable is the question ?
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Agree........ As mentioned, with a diff TB flow relation b/w TB,manifold and ports/heads at WOT will be different, which means VE also will be different... If compensated with a programmable or remapped ECU, gains should'nt be a problem, the magnitude of which is again based on how bad the OE TB setup was....
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.. all dynocharts I have seen are comparing enlarged TB to a stock TB which show very good gains but after hardcore modifications to the engine which really require the extra airflow mass and velocity and this is what you and me already know...
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totally agree