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BIG Throttle Bodies?
coozer - 19/1/09 at 04:13 PM

Anyone considered using the BIG bodies off a TL1000 on a zetec?

They are about 46mm i think and quite cheap on the bay.. About £100 for two sets. Just need joining together to make an inline set.

Steve

wilkingj - 19/1/09 at 04:36 PM

Bigger is not always better.

Unless you need that much air, your performance could suffer in other area's, making it less tractable in traffic / for normal driving.

Check all the options before parting with your money.

If its an out and out trackday car, then it would well be the Dog's Dangly bits.

Check that it slots in with the rest of the tuning of the engine.

Just my 2d's worth.

UncleFista - 19/1/09 at 04:44 PM

Dave Walker had a 2.3L Duratec in his workshop in November's PPC mag.
It was running 286BHP on......54mm TBs...

He had a bet with the owner that it'd drive like a dog, but after mapping it was well behaved and rather quick.

The point he was trying to get across was that you can run much larger diameter throttles with injection than you can with carbs.

Have a go and come back and tell us how it went

BenB - 19/1/09 at 06:09 PM

You can get away with big butterflies on EFi and if you used a cranked throttle arm you can remove the low-throttle problems.

Then again, there are recommended size TBs. Not sure the recommendation is for NA TBs but Forced Induction by Graham Bell shows recommended sizes for different BHPs. I did a little number crunching and worked out that it equates to 10 square mm per Bhp... Which means I should use a 45mm TB for my 160Bhp target. Trouble is the first TB I bought was a Rover200 48mm and the one I'm using is a RS Turbo 52mm I guess we'll see how intolerant EFi installs are to overly large TBs!!! That should be good for 210 blown BHPs and to begin with I'm using it on a stock 110Bhp ST engine!!! IE I did the usual thing of working out exactly what was required and then totally ignoring it!!!

MikeRJ - 19/1/09 at 09:12 PM

quote:
Originally posted by UncleFista
Dave Walker had a 2.3L Duratec in his workshop in November's PPC mag.
It was running 286BHP on......54mm TBs...


Then again my friends rally car was running 268 bhp from a 2.0L Mi16 with 42mm throttle bodies. They were actually 45's, but the engine builder had a cunning plan of fitting 42mm venturies in an effort to help low-mid range torque, and it certainly use to pull pretty well from about 2k RPM.

Being rebuilt as we speak with iron block, shorter stroke crank, lighter pistons and longer primaries on the exhaust manifold. so should be good for up to 9k RPM, and hopefully a bit more power as it hadn't quite peaked when they hit the rev limiter at 8.5k before!

The Dave Walker article didn't show a before and after torque curve IIRC which would have been interesting.

Jenko - 20/1/09 at 03:59 PM

You most certainly can get away with bigger TB's than the choke sizes in carbs....However, common logic says this will be depentant on your max bhp......

With bigger bodies you get much more air in at very light throttle, meaning jumpy throttle control, you also reduce the effective air velocity. Many of us are using 38mm GSXR600 TB's on engines of around 160bhp which seems perfect...loads of of low down throttle response, smooth....Bigger would alos work, and may possibly breath a little better at full power, but you have to consider how you drive the car......


If it were me, anything up to 170bhp, I would go with 38 - 40mm, up to 200bhp 42-45mm............

46mm on a zetec will work just fine, but I would say the low end performance would be better with smaller TB's.

PJ.

britishtrident - 21/1/09 at 07:18 PM

A while back I played with concept of using 4 Rover tintop plenum chamber throttle bodies mounted on their sides ie spindles vertical, with the throttle levers joined by rod linkages I got the idea from an old 1960's straight 6 cylinder Mercury 100hp outboard motor.