Throttle Body Size (post b30 manifold swap)
 

Hello,

I am toying with another idea for my cheap m52tu gains thread but this information or rather the calculator that I used to get it could be useful for those with m54 engines as well.

For those of us who have swapped to the m54b30 intake manifold on our m52tu/m54 engines the question becomes: what do we do about the throttle body size (63mm)that is clearly much smaller than the m54b30's (80mm). The thing is, we really havn't made the engine itself require more air like a cam or more displacement would do, we've just removed a big choke point (the manifold). Our head is identical to and therefore has the same intake port size as the m54b30. However, having smaller displacement engines means that odds are we still don't need a throttle body as big as the b30's. I was originally toying with the idea of modifying a b30 throttle body with the mechanical linkage and motor on my throttle body. I don't know how feasible this is without having both in front of me. I also now think that having an 80mm throttle body on our 2800cc engine is not necessary.

I ran some numbers through a calculator I found here:
http://dairally.net/daihard/chas/Mis...aiThrottle.htm

The output numer to pay attention to and the one that corresponds the best to real world conditions is the very last one labelled capacity index method.

Essentially, depending on mods, the size required via the last output calculation type ranges from 65mm to just under 70mm. However if the other output calculation types are factored into the decision then around 70mm is likely ideal.

Here are some screen-shots.

The first is no mods,
second is tuned exhaust,
third is with tuned exhaust and cams.

How did you figure the cam values?

http://www.usautoparts.net/bmw/engines/m52.htm

I realize its not perfect because its for an m52 engine which is only single vanos and the values may change slightly. However I played with the cam values and they did not significantly affect the outcome for most outcomes and did not change the capacity index method outcome at all. I couldn't find m52tu cam values, as far as I know, they are not published.

I'm now toying with how I can bore the throttle body. I originally thought I could do it myself with a drill press. Now I'm thinking that a drill press would work to bore it, but there'd be no way to cut the new throttle plate to the exact size of the bored throttle body without a cnc.
That means it's probably better to have someone do the whole thing. I have a feeling I'll be able to find someone that will do it for under $150 though.

Here is another one using shrick 264 cams for the cam values, as you can see it did not change the results at all.

interesting work being done and I appreciate these efforts!

I have a spare 330Ci/i DBW TB I'm looking at right now. I measure about 70mm inside diameter, I think the easiest & cheapest way to do what you want would be to alter a stock 330 TB into a manual operating TB. It would be easier IMO to hook up a cable, then to bore out another TB.


Good luck.

I doubt you'll see much of a gain with a bigger throttle body. The issue with the cam timing tables (and head) selected is they are based on single vanos motors. They have different intake and exhaust port sizes compared to the TU/M54 heads and double vanos motors have continiously variable cams, which mean no fixed cam timing.

Well the head values used are TU/54 values so that part is accurate also you'll see that 3 posts above yours I used the values for schrick 264 cams for an M54 and came to the exact same result. In-fact moving the cam values all over the map did not affect the outcome given the other variables. So I think this still holds true.

Rob, you measured 70mm internal diameter on the 330 tb? I got the 80mm value from another thread (the only place I could find it listed online). If so, then ya, it'd be back to plan "A" of modifying a 330 TB. That would also explain why e36 m52's gain 5whp or so going from 63mm to the ideal 69-70 after the m50 manifold swap and why 330's also have a bit to gain going up past 70mm which is also a bit small for them.

BMW going with the 63mm makes sense for me because it would have been a good compromise between the requirements of the 2.3 and 2.8L engines and given they were restricted in the intake anyhow, they saved money by sharing the part. I don't really get why the engineers would have used 70mm for the 330 if a slightly larger size would have been optimal. Though again, being that the heads are shared between the 2.5, 2.8 and the 3.0L Maybe that was the next restriction and the throttle body was left at 70mm to keep velocity up because more size was not needed.

Ice, I don't know if you are right or wrong, but I'd still test it to find out.

I think the very easiest way to do this would be to bolt up the perfectly fitting 330 TB to the M54B30 intake manifold. There still is no way to operate the TB with the gas pedal, you can only open it by hand at this point. Stick it on the dyno & hand operate it, it either makes power or it doesn't. If it works out, then fabricate your throttle linkage, if it doesn't; you didn't waste much time or money.

Great idea, the only concern is whether the computer needs the tps for proper running or if its only really necessary for adaptation values. I suppose if I could somehow leave the old throttle body hooked up to the wiring (if the wiring will reach) I could have someone open it at the same time to get the readings in there. Even easier would be if they use the same tps plug and sensor.

Hoveringuy tested the M54B30 tb vs the M50 and found next to no gain, but I'm just going by my previous experience, so I'm not 100% positive. I hope your right, I'd love for an extra 5whp/

I just re-measured, keep in mind I don't have my 6" digital caliper handy, so I'm using a measuring tape. But I know I'm within 1mm or less, front & back side are exactly the same, it's certainly no more than 70mm. It could be as small as 69mm, here's what I get: 2.75" X 25.4 = 69.85mm.

Like I said, bolt it up, & dyno it by hand operation. Either it gains HP, or it doesn't. I say it will, then add your cable operation to the 330 DBW TB.


Good luck,
Rob

But what about the Throttle Position Sensor, how will that work during a dyno where I'm only hand operating it.

This is the plug on an M52tu throttle body.

I don't know the answer, anyone else ?

Sorry try again, had a hell of a time pulling the pic from ebay, (would only let me save as html, had to print to pdf and photoshop edit before the upload worked)

By the way, Iceman, did hoveringuy ever dyno the difference between the two throttle bodies or did he just say that by the seat of his pants it only felt like 3whp or so. He could be right, but I also know alot of people that can't seem to feel gains under 10WHP

He dynoed if I remember correctly. You can look up his threads (I would, but I'm at work and time limited.)

No problem, ya I already searched and couldn't find a dyno of that comparison.

just bought a b30 throttle body from xixixi. We'll see what happens.

in for results

im very interested in the outcome :)