Throttle bodies
12-08-2005, 03:52 PM
#2
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The length of the inlet tract will affect the torque curve as will the radii of the bellmouth for the inlet trumpet. Longer inlets are better for low down torque and shorter ones are better for top end power.
12-08-2005, 04:03 PM
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Bloke i was talking to has got it all fucked up then, he's got a 1.8 8v GTI engine in a MK1 golf, made a shit hot job of making bike throttle bodies fit on a custom manifold, then he says he's made the runners as long as he can fit in the engine bay (around 13 inch's i think he said) so as to get as much top end power as he can as it will be revving to 8.5k 
surely they should be direct to head for top end power going by what you say? especially as it's an 8v and already has a decent amount of bottom end grunt
His fab skills are second to none but he's poorly advised by the sounds of it
surely they should be direct to head for top end power going by what you say? especially as it's an 8v and already has a decent amount of bottom end grunt
His fab skills are second to none but he's poorly advised by the sounds of it
12-08-2005, 04:14 PM
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To quote 'Forced Induction Performance Tuning' by A. Graham Bell
long runners will push up bottom-end power, but once past the peak the engine will fall flat on its face. Short runners do the opposite - they kill the bottom end and help the engine maintain power way past the peak
12-08-2005, 04:45 PM
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I mentioned this in another post recently but I remember the 1990's Renault F1 engine having variable length inlet trumpets that would telescope up and down with the engine rpm - it was awesome to watch and obviously the variability gives the best of both worlds.
The radii on the inlet trumpets affects the flow rate also. There are alot of variables you can tune.
The radii on the inlet trumpets affects the flow rate also. There are alot of variables you can tune.
12-08-2005, 05:08 PM
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i believe his inlet's tapered down from the TB's to the head, cant remember off the top of my head the measurements.
That Renault engine sounds awesome, would love to see that, same sort of thinking as variable vane turbos, although they havent taken off, perhaps issue's with high boost petrol applications i suspect.
That Renault engine sounds awesome, would love to see that, same sort of thinking as variable vane turbos, although they havent taken off, perhaps issue's with high boost petrol applications i suspect.
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12-08-2005, 06:06 PM
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Well i just spoke to him and it made 153bhp ATW @6900rpm which from a 1800 8v n/a isnt too bad in my book, especially when he did EVERYTHING himself, including mapping it 
and he says theres more to come cause its not running how he wants, this was the first dyno run after running it in!
and he says theres more to come cause its not running how he wants, this was the first dyno run after running it in!
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