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Discussion Starter #1
Can someone tell me how you remove the spindle from the large throttle plate on a LET throttle body? There appears to be a cap over the end of the spindle with 3 small indentations in it - the opposite end has got the spring/return mechanism on it. How do you remove this cap? I don't want to start trying to prize it off and break the casting:confused:
 

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Discussion Starter #3
I want to rebore the housing and profile the spindle and fit a bigger plate - someone must have done this before?
 

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is there really any need for this on a blown engine? the only reason i can think of for increasing the throttle body bore would be to get more air in but the turbo is doin all the work with regards to supplying the engine with air aint it.

fair enough on a N/A engine where a larger throttle body would be less of a restriction so more air could get in the bigger diameter but on the turbo its gettin forced in anyway so....

unless it would help in reducing lag a bit ????

rodgerq
 

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Ian,

similar to what Regal offer? I don't know of anyone who has done this to a LET - although it is popular with the XE and V6
 

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rodgerq said:
is there really any need for this on a blown engine? the only reason i can think of for increasing the throttle body bore would be to get more air in but the turbo is doin all the work with regards to supplying the engine with air aint it.

fair enough on a N/A engine where a larger throttle body would be less of a restriction so more air could get in the bigger diameter but on the turbo its gettin forced in anyway so....

unless it would help in reducing lag a bit ????

rodgerq
I thought anything to increase efficiency on Turbos helps power??? So doing the spindle would be a good thing???:confused:
 

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Discussion Starter #7
Not_Too_Fast! said:
Ian,

similar to what Regal offer? I don't know of anyone who has done this to a LET - although it is popular with the XE and V6
Well I thought I'd try to increase the area as much as possible as it can only help. How much do regal charge for a modified throttle body:confused:
 

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imcsherry said:
Well I thought I'd try to increase the area as much as possible as it can only help. How much do regal charge for a modified throttle body:confused:
Something silly like £150 hang on I'll check....
 

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At high airflow rates, any obstruction is going to cause a pressure drop across it. It doesn't matter whether the starting pressure is atmospheric pressure or 0.6 bar, you'll still lose some pressure across the throttle flap. So increasing the throttle area should have a beneficial effect.

BTW I suspect the cap on the end of the spindle is to stop the boost pressure blowing out through the hole.:cool:
 

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They charge a lot, Regal was over the £200 mark.

As far as I know, the C20XE share the same throttle body as the C20LET, well mine look like they do. Dosn't the Haynes say anything on removing the spindle. I've never removed it, all I can say is be checky and see if Courtneay or Regal will shed any light (I doubt it).
 

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According to EPC they are two different part numbers:

LET Throttle 90423360
XE Throttle 90448590

However it does use the same drawing for both, so the differences may be limited to sealing the spindle against the boost pressure.
 

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Discussion Starter #13
The XE has an extra return pipe at the top of it (I'm not sure what its for) otherwise they are identical.
 

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Do some measurements before you waste your money.

Buy, borrow, steal a manometer and connect it up before and after the throttle. It will show you the pressure drop across it. Compare this with the rest of the intake channel to find the big restriction gremlins.

You can also make U shape water manometers but you have to be carefull under manifold vacume of it sucking the water out!

Or a pair of accurate boost gauges.
 

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I think the extra pipe is for crankcase ventilation - on the LET this goes into the turbo inlet.
 
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