[chetanhanda]

Either u have aftermarket cams, or ported polished heads, valve angle job and corresponding headers etc the stock TB may possibly be good enough.
hey bother dont with this if you have stock engine unless you only want a more sensitive throttle response..
seen some mods with air filter and enlarged TB only while everthing else stock...normal cams, no polishing, valve job,no headers or forced induction.

this doesn't give you that much power it just makes your throttle more sensitive,
heres the argument - I have seen ppl say "dude I bolted on a big TB so it pulls in more air so the ECU puts in more fuel so = more power"
sure you felt the surge when you drive dude thats only becoz at that throttle plate angle the air you are drawing in is more becoz of the larger dia.
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.

think of VE.. (im trying to simplify it in layman terminology, ther eis much much more to this ...)
what the hell is this ? ideally theoratically if an an engine is 100% efficient, so theoratically it pulls in air fuel mix
= to the displacement of the engine at WOT.Since the 4stroke engine has has one intake stroke for every 2 revolutions of the crankshaft we can suck in x units of air= displacement of the engine in 2 revolutions.
so to find the qty of air sucked in we multiply the displacement by 1/2(the engine speed) assuming it is 100% efficient for simplicity sake. so our Volumentric efficiency is 100% but in real world the engine may acheive say 50% efficiency..
for now if we want to increase the air flowing through our system we will use porting polishing, crazy cams etc etc etc and later on use a turbo/supercharger and run the engine at very high revs and increase airflow than what the stock TB was designed to handle.
A stock engine may have a TB size perfectly port matched for this mass and velocity of air flow, so unless we use crazy cams etc etc or forced induction we are in no way increasing the airflow. If the OEM TB was obstructing the airflow to such an extent that the VE was reduced to
(50-x)% then it makes sense to upsize the TB to remove this bottleneck.. Im sure car manufacturers have taken care of this already... if u have a stock engine with no other mods why upsize your TB ?

bolting on TB on stock cars and saying the ECU pumped more fuel got you more power doesnt make sense to me...
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 throttle position.
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...

Ideally OEM guys design the engine for driveability and mileage ,you could say they distributed the entire range of the power in the throttle pedal so its not so sensitive to slight inputs during normal driving.
so a slight throttle input will pull in a certain qty of air which will make the car accelarate gently in a civilised manner, what a larger Tb would do is increase the amt of air for the same Throttle position, as a result 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 ?
the slight obstruction due to the butterfly type of throttle plate caused in the OEM TB will be minmised slightly due to the larger bore TB so it may help at these WOT conditions..

if I can put it like this .. what u are doing is fooling yourself, you could wear 10kg wt on ur shoe and drive the car, sure you will floor the throttle more as compared to without the weight, so you get the throttle response without the cost of new TB...
upsize this if this is a bottleneck after upgrading the airflow otherwise its good for just a sensitive twitchy throttle feel, bolting on a TB without supporting modifications will not make large power gains(Im assuming who ever bolts on a large TB is also port matching it to their engine correctly)

(also if we think of velocity of airflow, its much higher when passing thru a narrower pipe as compared to extreme super large dia TB port, this may not be felt so much in case of fuel injected systems in some cases but we can keep this thought in the back of our minds..)

if you have plans for crazy mods exceeding what the OEM TB was designed go for it but till then it wont make big bhp gains on its own as just a bolton only...

guys what u think ?

[Psycho]

Originally Posted by chetanhanda

(Im assuming who ever bolts on a large TB is also port matching it to their engine correctly)

(also if we think of velocity of airflow, its much higher when passing thru a narrower pipe as compared to extreme super large dia TB port, this may not be felt so much in case of fuel injected systems in some cases but we can keep this thought in the back of our minds..)

if you have plans for crazy mods exceeding what the OEM TB was designed go for it but till then it wont make big bhp gains on its own as just a bolton only...

guys what u think ?

1) Well what does TB have to do with Port Matching?

2) If the second part of your understanding was true why would we need performance filters? The manufaturers would have thought of that too wouldnt they?

3) Larger TP means more flow means lower HG hence more load for the same throttle position, hence ECU uses the load map to up the fuel. More air & More fuel for the same throttle position = More power and a quicker response

4) You ought to see some cars here flying using twin throttle bodies and ITB's

What you are all missing out on is the combination effect that all mods have on a car and not just one. You cannot work out your ABS and say the rest of your body as good as your ABS.

[ananthkamath]

that explanation makes sense, do you have access to any test data which indicates the same. Dyno results etc..

[mclaren1885]

Psycho , sideways , ford rocam should visit this thread a lot more .. Wonder whats keeping them away ???

[chetanhanda]

Originally Posted by Psycho

1) Well what does TB have to do with Port Matching?

Everything, if you try to fit a super sized or heavily ported TB to a intake plenum you got to match the intake plenum to the TB and the plenum to the head, whats the use of a huge TB when the plenum and head(intake ports) still has tiny ports ?
(just an example... this is not a honda specific thread, its just an example e.g think of an Edelbrock 70 mm TB for a D16 requires port matching, the same principal applies to all other engines..)

Originally Posted by Psycho

2) If the second part of your understanding was true why would we need performance filters? The manufaturers would have thought of that too wouldnt they?

I think all of us have covered this part in detail... but just to reiterate - it would be an overkill to have huge performance filters with oversized TB with stock internals, but if you are doing something crazy - throw the OEM stuff out - get a proper heat sheilded/ducted CAI and big TB's

Originally Posted by Psycho

3) Larger TP means more flow means lower HG hence more load for the same throttle position, hence ECU uses the load map to up the fuel. More air & More fuel for the same throttle position = More power and a quicker response

I would say only more quicker response only at part throttle conditions equivalent to being a little heavy with the foot on the throttle pedal and not more BHP, maybe minute BHP gains at WOT ,(as mentioned in my earlier post) but will it be noticeable ?

with only a enlarged TB modification (for part throttle closed loop) you pull more air for the same throttle position x% i.e send a MAP signal to ECU which is the same which you would have got when you had floored the throttle to (x+n) % with original TB, so you get the same IPW for the same rpm for the same MAP signal but at lower throttle position (bcoz same angle of butterfly lets in more air) there is a lot more calculations being done but just to make it simple..
and regarding WOT here is my original post...

Originally Posted by chetanhanda

but hey the TB may not 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 ?
the obstruction due to the butterfly type of throttle plate caused in the OEM TB will be minimised slightly due to the larger bore TB so it may help at these WOT conditions..

Originally Posted by Psycho

4) You ought to see some cars here flying using twin throttle bodies and ITB's

Psycho I beleive you, they must be 100% flying, but are they soley flying based on their ITB's and twin throttles only?
I dont think so, they may definately have other mods which have increased their stock VE by: high lift/duration profiles, porting,polishing, crazy angled valve jobs, good header designs, tuned intake lengths, free flow exhausts,advanced custom ignition and fuel curves, lightened flywheels, forced induction etc etc, lightened body etc etc etc.....
Its after some of these mods have been done that the need for a supersize TB is reqd...
stock internals + big bore TB = same power but snappy throttle response, and maybe 1 bhp gain at WOT... (if the the stock OEM TB was very badly designed)

Originally Posted by Psycho

What you are all missing out on is the combination effect that all mods have on a car and not just one. You cannot work out your ABS and say the rest of your body as good as your ABS.

exactly !!
exactly what Im saying, enlarged TB is not a huge power delivery addon by itself , it creates huge power if it is there to aid the increased air flow requirements of a modded engine which has requirement for increased airflow..

[chetanhanda]

Originally Posted by ananthkamath

that explanation makes sense,

thanks dude..

Originally Posted by ananthkamath

do you have access to any test data which indicates the same. Dyno results etc..

hey ananth.. 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...
and also what Ive seen is the people who do dyno runs are not riceboys and are hardcore technical enough to mod their engine and then upsize TB... difficult to find dynocharts with only an enlarged TB as the only standalone mod and waste money on a dyno pull...
but it would be nice to see one...

[rdkarthik]

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.

i guess we do have a few retards around

A stock engine may have a TB size perfectly port matched for this mass and velocity of air flow,

Atleast in India, i dont think many cars have ports,TBs and manifolds matched.

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

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.

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...

The Ford escorts and if i remember correctly the early versions of opel astra had alpha-N

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 ?

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....

.. 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...

totally agree

[chetanhanda]

Originally Posted by rdkarthik

i guess we do have a few retards around

Originally Posted by rdkarthik

Atleast in India, i dont think many cars have ports,TBs and manifolds matched.

wow.. thats news to me karthik
port matching is reqd

Originally Posted by rdkarthik

It cant be stock power of higher RPM at lower RPM ..... For a given condition, with more air its only z that changes.....

agreed.
exactly dude...!!
thats what Im saying the higher "z" is returned for more air if only the TB is enlarged.... see below

Originally Posted by chetanhanda

with only a enlarged TB modification (for part throttle closed loop) you pull more air for the same throttle position x% i.e send a MAP signal to ECU which is the same which you would have got when you had floored the throttle to (x+n) % with original TB, so you get the same IPW for the same rpm for the same MAP signal but at lower throttle position

its just that the higher "z" is made available at lower throttle position
becoz the corresponding MAP at this throttle position is = what was available earlier with OE TB for higher throttle position..

Originally Posted by rdkarthik

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 .

Ok,
Agreed only if the intake subsystem design is totally diff then definately it has as a say on VE.
But if we just enlarge the OE TB "in place" as posted .. from say 56 to 60mm then definately all the characteristics are the same and only the TB size changes.

Originally Posted by rdkarthik

Its different on MAF systems though.

sure, agreed..
(I was referrring specifically to only MAP everywhere in all my posts)

Originally Posted by rdkarthik

The Ford escorts and if i remember correctly the early versions of opel astra had alpha-N

ok, and thanks for pointing that out.
I was not aware of Ford escort and Opel Astra.

Originally Posted by rdkarthik

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....
totally agree

agreed !!

[GTO]

Just read through this thread again, and gotta say...its awesome.

This thread = Sticky!

[Deepz]

Hi guys,very informative thread..good job..Any suggestions for increasing performance of RPM's mid-range, since its the most useable range in everyday driving? Its ok if high-end remains same also..(Sorry if posted inwrong thread)..thanks..

[mclaren1885]

Originally Posted by Deepz

Hi guys,very informative thread..good job..Any suggestions for increasing performance of RPM's mid-range, since its the most useable range in everyday driving? Its ok if high-end remains same also..(Sorry if posted inwrong thread)..thanks..

Get headers calculated accordingly. Get a cam that gives you the kick in this range.

[veyron1]

Nice thread. As said before, loads of info. Just a thought. Calculating appropriate injector pulse widths at wide open throttle, or appropriate I/T-E/X cam lobe angle for a given displacement w.r.t R.P.M load, or any other parameter for that matter, is well-nigh impossible without a dyno. Hence, most of this knowledge, although very, very, useful, cannot be put to actual practical use over here in India.

Secondly, saw Karthik's inputs on alpha-n. The Escorts and Astras had TBI, not MPFI. At least the ones sold here. So, taking into account the MAP readings at closed throttle could someone elaborate on the actual priciple or effects?

[Ford Rocam]

Originally Posted by veyron1

Nice thread. As said before, loads of info. Just a thought. Calculating appropriate injector pulse widths at wide open throttle, or appropriate I/T-E/X cam lobe angle for a given displacement w.r.t R.P.M load, or any other parameter for that matter, is well-nigh impossible without a dyno. Hence, most of this knowledge, although very, very, useful, cannot be put to actual practical use over here in India.
?

It is possible, please dont ask how i will be doing it, but all i can say is wait & watch!

[chetanhanda]

Originally Posted by veyron1

Nice thread. As said before, loads of info. Just a thought. Calculating appropriate injector pulse widths at wide open throttle, or appropriate I/T-E/X cam lobe angle for a given displacement w.r.t R.P.M load, or any other parameter for that matter, is well-nigh impossible without a dyno. Hence, most of this knowledge, although very, very, useful, cannot be put to actual practical use over here in India.

100% right !! loading type dyno will be the best..but for NOS type of apps the acceleration type would be better
but I think we should wait and see what Ford_rocam is upto ..

Originally Posted by Ford Rocam

It is possible, please dont ask how i will be doing it, but all i can say is wait & watch!

Originally Posted by veyron1

Secondly, saw Karthik's inputs on alpha-n. The Escorts and Astras had TBI, not MPFI. At least the ones sold here.

ok so they were even more primitive ..

Originally Posted by veyron1

So, taking into account the MAP readings at closed throttle could someone elaborate on the actual priciple or effects?

sure .. but can u let us know what are you looking for specifically ?
I mean... principle/effect WRT : ignition timing, fuel,valves,cams, etc ?

[veyron1]

Originally Posted by chetanhanda

sure .. but can u let us know what are you looking for specifically ?
I mean... principle/effect WRT : ignition timing, fuel,valves,cams, etc ?

Ok. Here goes. Speed/density metering or mapping is usually dependent on engine speed, air density and MAP.

Alpha-n is the advanced version for mapping which can take in more radical cam profiles because it reads from the engine RPM and throttle body positioning only, bypassing the MAP.

Now, both systems/routings are prone to vacuum errors/stats.

The Escorts had TBIs. How exactly did the alpha-n system "improve" the combustion characterisitics? AFAIK, MPFI's have much more precise fuel metering, correct?

Ok. Now for details. Let's have in detail the effects on cam profiles for alpha-n (since that's what's used for racing applications- we know that poppet and stem height are in direct relation to lift; so we'll go into that later),and ignition timing (both ignitor mapping and delco alteration-for the Escort). And how exactly do both of them alter IPW at WOT (assuming WOT is at 100%, both systems are giving 100% fuel flow)....

Simply put, let's have in detail the differences in ACTUAL practical applications, and how-to's...

P.S-Nice to know about Autozone. They are regulars in ACI ad-section...and let's wait and watch, eh? Mumbai was supposed to get 2 dynos quite some time ago; still nada...