Mi16 Conversion - Headroom...?

[rgp205 2]

I'm planning an Mi16 engine conversion sometime in the future - have the engine, will take my time rebuilding it to the spec I want first, however I'm going to put a fiberglass bonnet on the car now and was thinking of going for an auto bonnet for more space (want to run TB's or 45's), but I'm not sure if the auto bonnet provides extra space in the right area... maybe the bulge is too far back and I'll end up having to cut it anyway... anyone know for sure...?

[johnnyboy666 195 1 Cars]

the auto bonnet does give a little extra space. I think 45s should be alright, couldnt comment on tb's though. you could always cut away a bit more of the bracing or use a little spacer to lift the rear end of the bonnet up a bit. Sometimes looks weird tho depending on how much you rise it by

mind you if its gonna be fibreglass anyway you could just get a skin and use bonnet pins?

Edited April 25, 2012 by johnnyboy666

[Anthony 1,003]

Auto bonnet adds height above and behind the engine, whereas where you really need the space when running TB's is in front.

 

Magnum Motorsport used to do a fibreglass bonnet for just this purpose with a distinct raised section towards the front, although even with that you're still fairly limited what trumpets you can run assuming that it's a typical Jenvey type setup.

 

 

Maybe not entirely clear in that picture, but it's the first one that I found.

[petert 588]

Plenty of people, including myself, run TB's under the standard bonnet. The trick however, is to get cold air in, not draw off hot air from the radiator. You see this poorly done on many 205's.

[welshpug 1,661]

a decent inlet manifold and a dropped/shortened radiator is what you need

[engine killer 6]

you can have short trumpets under normal bonnet.

 

as we have air-conditioning system, a condenser sits right between cooling fans and radiator which gives much lesser room but still fits alright.

 

as Peter mentioned, you need a cold air feed.

 

modifiying the slam panel seems the easiest solution.

 

as mine was firstly designed/used for socks, so cutting it for more room for sausage was the easiest.

Edited April 26, 2012 by engine killer

[Simes 248 2 Cars]

My tb's fit under a standard bonnet, cut slam panel and lowered rad.

[rgp205 2]

Thanks for all the replies folks, seems going for a standard fiberglass bonnet and modifying the slam panel / rad is the way to go...

I guess if TB's fit under a standard bonnet then there'd be no problem fitting a strapped 'glass bonnet...?

[Anthony 1,003]

Jenvey's do "fit" under a standard bonnet with the usual short trumpets, but usually they won't with optimal length trumpets.

 

That is part of the reason why Sandy and Colin did their throttle body setup the way they did as I understand it, so that you could get the required induction length without having the filter hanging out of the front of the bonnet. I'm sure Sandy will have some back to back figures with different inlet lengths, but as an example, a friend of mine with a 2.1 GTi-6 gained 16 lbft throughout the mid-range by running longer trumpets - but there's no way of doing that with a standard bonnet, so he ended up cutting a big hole in it and adding a bulge.

 

To put that difference into context, that's almost the difference in torque between a 1.6 and 1.9 8v engine gained just by adjusting the trumpet length!

 

Don't confuse Jenvey supplying something designed for easy bolt-on fitment into a standard car with something optimal. To use long trumpets, you'll either need to angle the throttle bodies downwards by adapting/changing the inlet, or you'll have to modify the bonnet for clearance.

[rgp205 2]

Can I source an angled inlet manifold somewhere or do I need to get one made up?

The Omex kit states the inlet manifold is angled at 30deg so the trumpets are parallel, is that sufficient or would I need more angle?

I've seen trumpet lengths of 20-90mm, guess longer is better then?

[welshpug 1,661]

You need to speak to Colin satchell about an inlet that'll suit a decent tract length in a 205, he has done them in bike body and DCOE pattern.

[Simes 248 2 Cars]

Omex kit comes with jenvey inlet manifold and 90mm trumpets

My air filter does rub against bonnet and the support mesh rubs on the trumpets. I'm going to cut some of the bonnet reinforcement away.

 

[Simes 248 2 Cars]

90mm trumpets are the best compromise.

Longer would give more torque but would, as mentioned protrude through the grill.

[rgp205 2]

I don't mind trumpets protruding through bodywork, she's a competition car, she doesn't need to be pretty (although she is of course!) ;-)