I was talking to Barbz a few weeks back about upgrades to my car - he suggested boring out the throttle body for more flow

However I have heard that there is a bolt on BMW swap - which is bigger (yet to confirm model) and flows alot better

If I swapped the throttle body what would need to be done about TPS etc or are these all pretty much the same

I realise it is a bit vague in the question, but what else is changing the throttle body going to stuff up?

cheers

Loooads of the coupe/bosch parts are robbed from BMW's so its likely compatible, just get the connectors im sure you could sort the wiring then.

Model dependent of course, but i'd be hopeful

apparently the BMW 325i E30 throttle body is a bigger version of the same I am told on the integrale forums.

Can anyone confirm this?

I would need the BMW TPS plug as well then I guess

The TPS probably works in the same way as most do.

Still don't understand why you want the hassle of this, when the stock throttle body will outflow the head and not actually give you any more power, but worse driveability

Begbie - basically following barbz advice. I know the standard ports flow 136cfm each do you know what the factory throttle body flows given it has the butterfly in the centre?

maybe GC has measured one?

V.

I don't know what the throttle body flows in cfm, but if it can do 400 / 500bhp without any issues, i fail to see the point in creating more work for yourself, when the head will be the restriction, not the throttle body

Totally agree. TB will out flow the head.
I see so many people fitting bigger TB's to engines, when the real problem is the head itself.

Andy.

So by going on GC calculations, the throttle body 52mm (std coupe, std integrale, std tipo) will flow 250CFM, which is more than enough!

Standard throttle body is 56mm which is good for just over 300bhp, after that it becomes a restriction. This does not mean that it still won't deliver.
Yes for sure if you bolt on a big enough turbo you can force the air through any sized hole and still see good power.
The Coupe TB is more restrictive than the 'grale item as it has a shroud in it to give it more progression at small throttle openings, you could maybe grind this off and then re-bore.
From what I have read of GCs work his knowledge of turbocharged engines is a bit lacking and still in the dark ages, he also tests at 10" depression which is very low and not a true representation for turbocharged applications.

I am hoping that Mr Saint will one day heed all the advice given to him over the last few years and finally realise that getting good honest power from an engine does not cost pennies, there are no cheap short cuts, you have to splash the cash and modify properly or replace many of the components so that they are in harmony with one another.
I think that maybe by the time it has sunk in we could be all very very old.....

The only real way to find out exactly what effect it will have is to dyno it.

Yes, that is very true. All the CFM talk is only a very educated pointer as to what will happen, sometimes the dyno, the road and the track will tell otherwise.

I don't know the answer to whether this throttle is any use or not. But in general you don't make all the components flow the same amount if anything you would want them to be staggered in the way that the throttle will flow more/be less restrictive than the plenum chamber and the plenum more than the inlet manifold etc. because you want to be absolutely sure that no intermediate component is flowing less than its preceeding component. I think you all know this to be true because you already know that the std throttle flows more than the head and it has been designed that way in the first place.

You don't make the ports so they will flow the exact amount of air to support a particular amount of power you should make them so they will flow more than that in exactly the same way.

Gralecoupe, I appreciate the technical info you gave, I couldn't find that data. however another forum member contacted me yesterday via PM about bigger throttle bodies so thought I would look into it.... and I was under the impression this was a discussion forum. , specifically tuning

So if I take my 2 pennies rather than 1 are you suggesting there is an expensive of the shelf TB we should buy?

But why not ask the question



Start with a cage containing 5 monkeys. Inside the cage hang a banana on a string and place a set of stairs under it.

Before long a Monkey will go to the stairs and start to climb towards the banana. As soon as he touches the stairs spray all the other monkeys with cold water.

After a while another monkey will make an attempt to climb the stairs to fetch the banana – with the same result spray all the other monkeys with cold water.

Pretty soon, when another monkey attempts to climb the stairs the other monkeys will try to prevent it. Now put away the cold water, remove one monkey from the cage and replace it with a new one. The new monkey will see the banana and attempt to climb the stairs. To his surprise and horror all the other monkeys attack him and after another attempt and attack, he knows that too climb the stairs will result in an attack.

Next remove another of the original 5 monkeys and replace it with a new one. The new comer goes to the stairs and is assaulted the previous new comer also takes part in the attack with enthusiasm. Replace a third original monkey with a new one then a fourth and fifth.

Every time the new monkey takes to the stairs, he is attacked. Most of the monkeys that are beating him have no idea why they are not permitted to climb the stairs or why they are participating in beating the monkey. After all the monkeys have been replaced none of the monkeys have been sprayed with cold water, never the less no monkey ever goes to climb the stairs to retrieve the banana….Why not? Because as far as they know that’s the way it has always been done around here.

Why not be the monkey that asks the question, your right, I will always ask and it won't sink in

Cheers

True, but then when you have upgraded the head then you have to upgrade the TB and so on and so on.....

nissan 200sx has 50mm as standard and those guys use it over 450hp. our is 56mm and was it tipo 1.8 that has "grale style" intake manifold and 60mm t.body. what ever, I think that if going over 500hp put your money on new t.b. otherwise .. dont think it make any difference really.

Cheers guys - maybe it was because I was getting cams off him that Barbz suggested it. But I will leave it alone for now, till I get the head work done

"You're right, I will always ask and it won't sink in."

Hope this was a typo!

So what you are saying is that you shouldn't follow what everyone else does if there is a better way that is different?
It's a fair comment and one I wouldn't disagree with, but only if the old ways were wrong and can be improved upon by other methods, sometimes they can't and most basic tuning principles have been around for years, gasflowing the head is one of them, Beggars hit on it earlier - no point in uprating the TB if the head hasn't been flowed.

Too many guys depend on forum gossip to tune their cars, although there is some good stuff posted, really 80% of it is bollocks, it takes someone with experience to tell who is bullshitting and who isn't.
Me? I read it, it's entertaining, good for a laugh, useful for picking up parts, but If I want to tune an engine properly I read a book.
Even then as you know, sometimes you've just got to go ahead and give it a go and accept it if you fail, i've seen few of my own!

I will keep asking questions, some does sink in though

You should always ask why. If the answers given are logical and make sense then carry on doing what has been done. If the answers are "because thats the way we have always done it" then look at alternatives and make your own call.

I don't recall having asked this question ever before, and the replies seem logical as to why it's not worth it, so i'll keep doing it the way it has been done, and leave it at that.

to quote you "but only if the old ways were wrong and can be improved upon by other methods" the only way to know is ask, don't want to be a sheep aboout it.

Anyway - back on topic before I get banned

Surprisingly car manufactures often use one part across multiple models and perhaps that part isn't ideal for the application, just cheaper

Maybe this would be interesting for those guys with flowed heads, you suggested at 300bhp it becomes a restriction in your first post, so as always i'll ask.

Cheers

Hardly Paul for asking a question and being, umm... creative with the come back, would take far more than that for a banning

O/T - Chippy, any sign of that base map please?

Yep, always ask why, sometimes you make a nuisance of yourself, but if it gets you the knowledge then so be it.

Throttle size is down to what power output you are aiming for - if someone sees 450hp from 50mm then you have to question if it was a BS pub talk figure or if the guy wouldn't have gained another 20 horses by upgrading to say 60mm, like I said, if you have a big enough turbo you can force the air through, it's not correct in my book though and will leave you with a very laggy motor, but it still gives the figures to tell down the pub.
It's not down to outright power either, what about driveability? Is it a street car? Do you need it?

So many variables!

In my road car, barring the turbo (standard 'bigger' T3) I upgraded everything I could that air passed through and ended up with 100bhp more, less lag than a standard car and less than a standard 20vt (I used to own one).
I could have just fitted a bigger turbo, had more power, more lag, less MPG and less driveability, but it isn't what I wanted as it's a road car.

Boring out the TB isn't expensive, there are online companies who do it for $100 - $150 and they are probably closer to your end of the world than ours.

A good head job is the daddy though, how many modifications can you do to a car engine that only have plus points and no down sides? Not many.....

Still having problems getting Motec to run on my laptop, I think it's Vista that's cocking things up, I've had a computer whizz around to look at it and both methods we used have failed so far.

Let me know when you are ready for it (2009? ) maybe I will have sussed it by then....

please show your head development and throttle tests please.

Rich

I prove my work in practice - on the dyno, on the road and at the track, not in theory, you want to see a power curve?

So has GC too, but the link you posted earlier was from a theoretical view point, no actual throttle body was tested, there was no throttle plate and spindle taken into consideration, no steps on the inlet, no shroud over the top of the throttle plate which does exist on the Coupe TB. It was based on a test on a straight tube at low vacuum to put a point across which it did - very well.
I know you're his biggest fan and I have respect for him too, but i'm not blinkered and can remain objective, everyone has their strengths and weaknesses - you can't be good at everything. There aren't many people who you can send a Fiat/Lancia engine to for re-building, or a head for gasflowing and building and (money aside) relax in the knowledge that it will be done properly to 100%.

If you want to prove how much a Coupe TB throttle flows then you must give him one and everything else it is directly connected to and get him to test it.

This is my last post on this (GC) subject as I refuse to get further into a debate about somebody else.

What modification have you done to the engine of the road car? I would be very interested to know.