Throttle Bodies

[turbosei]

Having read a few of the posts on here it's clear that there is a wealth of knowledge on this forum.

I'd read elsewhere a few criticisms of the throttle body installation on my Seicento and would really appreciate your opinions.

This is a link to a large res picture of my engine:
Engine pic

The engine is a 1.2 16v from a Fiat Punto that would normally put out 85bhp and about 75lb.ft. I'm getting around 120bhp and 90lb.ft in a flat torque curve (Rolling Road graph)

The throttle bodies are from a Suzuki Hayabusa and IIRC are 40mm. The engine has been fully lightened and balanced, but is running standard cams.

[vrooom]

THat is nice. i like it yummy throttle bodies

[denisb]

No air filter!!!!

Otherwise looks about as good as you could get without major engineering/bodywork modification/expense.

[YarisSi]

That is very cool.
Why is there a benefit over normal injection though? Or have you done a lot of other stuff? Where did you get a manifold to make it possible to connect it to engine?
Si (no mech knowledge)

[turbosei]

I had a custom manifold made up by Retro Motorsports in Harlow.

I've had one person comment that the torque was 'appalling' and the installation completely wrong, which was my main reason for posting here. I'd be interested to know whether a 15lb.ft increase in torque is 'appalling' and whether there are improvements that could be made to the installation and what they would be.

Thanks for your comments so far guys.

[joospeed]

90lbs torque from a 1.2 16valver isn't great to be fair .. only 75lbs per litre is below what you would expect for a well tuned 2 valver.

however if the rest of the engine is relatively stock then it's pretty much what you would expect.

you have plenty of room for playing with the trumpet lengths, and the install and engine bay in general looks great - very neat.

I'd second the desire to have an air filter .. you'll quickly cause enough damage to lose power very soon without a filter. get a large free flowing one and you'll not sacrifice any hp, in fact you can use the filter casing top as a positive waveform reflection point so further tuning the torque curve.

all in all a great looking engine, well done

[turbosei]

joospeed said:

90lbs torque from a 1.2 16valver isn't great to be fair .. only 75lbs per litre is below what you would expect for a well tuned 2 valver. however if the rest of the engine is relatively stock then it's pretty much what you would expect. you have plenty of room for playing with the trumpet lengths, and the install and engine bay in general looks great - very neat. I'd second the desire to have an air filter .. you'll quickly cause enough damage to lose power very soon without a filter. get a large free flowing one and you'll not sacrifice any hp, in fact you can use the filter casing top as a positive waveform reflection point so further tuning the torque curve. all in all a great looking engine, well done

The head is flowed, but because of the way the cams are carried on the Punto engine it hasn't been possible to modify those. The bottom end is balanced and pistons and flywheel are lightened. It happily revs to about 8500rpm.

Does anyone know how to calculate the ideal trumpet length for the engine?

Also, what sort of torque would be considered good for a 1.2 16v?

Finally, assuming no budget restrictions what would be the perfect setup?

>> Edited by turbosei on Thursday 19th May 22:52

[350matt]

try this to get you started:
INTAKE RUNNER LENGTH ii
ECD = Effective Cam Duration
RV = Reflective Value = 2 for 2nd reflection 3 for 3rd etc – the earlier the reflection = the stronger the tuning
ECD = 720 - (Adv. duration - 30)
Speed of sound = 396m/sec
intake runner length = ((ECD/360) × (1/(tuned rpm /60))* speed of sound)/(2*RV)
( ((470/360) x (1/6000 /60))*396) /(2 *6) = 0.43mtrs


Matt

[denisb]

Torque. Based on my engine (Toyota 1.6 16 valve) but seasonally adjusted for your smaller engine I would want around 95-100 lbs minimum.

[turbosei]

Does anyone know of a good airbox supplier?

I know Reverie do them in CF and GRP, but I was hoping to find something a bit cheaper if possible.

I think the total intake tract length is about .43m, or not far short of it.

Excluding forced induction, what would you guys recommend to maximise torque from a 16v engine?

[350matt]

Uuuuum, my example is just that, an example, you should re-work the calc with your own cam duration and peak power rpm figures

Matt

[YarisSi]

350matt I don't understand this reflection value. I take it is the number of times the air bounces of the valve before it opens?
Actually I got no idea. Only think I have managed to pick up is longer trumpets are better because at two different points will it be tuned. Could you explain it or point me in the direction?

[350matt]

The reflection value is the number of time the shockwave will travel up and down the intake tract, every time it reflects off the open end of the tract / trumpet it reduces in strength.
The trick to applying it is to have the correct length inlet for your camshaft and desired peak power engine speed. The timing of pulse can be arranged so it draws in fresh air just as the inlet valve opens so creates a supercharging type effect
see :

http://auto.howstuffworks.com/question517.htm

Matt

[YarisSi]

Thank you. I'm going to have to study this a bit.

[turbosei]

Cheers, funnily enough I found that link last night as well!

Just trying to find the spec of my camshaft.

Am I right in thinking that an airbox would act as another point of reflection?