want a cheap(ish) BIG throttle body.

[annoyingrob]

I have this idea of putting a 2nd throttle in front of my turbo's intake, after seeing a SC'd M5 do it to eliminate surge with great results.

I'm looking for something with a 4" OD, so I would assume around a 90mm ID, and preferrably just a round coupler on both sides. TPS is unnecessary.

Anyone know of a good source?

 

[Wiisass]

Aren't q45 tb's about that size? It won't have round spots to use couplers on both sides, so you might need an adapter plate, but i don't think i've seen anything exactly like you're talking about. But I also haven't looked for that.

And isn't that something that they used to do on turbo F1 cars back in the day? I forget all the reasons for it though. How are you planning on controlling it?

 

[selfinfliction]

check the ford lightning TB's, iirc they are 90mm. should be able to get a used one for $50-$60

 

[annoyingrob]

Aren't q45 tb's about that size? It won't have round spots to use couplers on both sides, so you might need an adapter plate, but i don't think i've seen anything exactly like you're talking about. But I also haven't looked for that.

And isn't that something that they used to do on turbo F1 cars back in the day? I forget all the reasons for it though. How are you planning on controlling it?

Q45 TBs are 90MM OD, which is close, but I want something like 102mm OD, with a circular fitting inlet and out.I think this is going to have to be a custom thing after some searching.

Here's a picture of a similar Dinan SC kit in an older M5. If you look closely just behind the BOV piping, there's a 2nd throttle installed in the intake just before it goes into the SC.

I was planning on controlling it purely off the original throttle linkage with another cable. Calibrate it to open up at say 30% throttle, being fully open at full throttle. The reasoning behind this being as I close the throttle, the turbo starts sucking on vacuum before it has a chance to back up, and surge.