Home made supercharger setup - what's needed?

[crofty1984]

Idle moment at work.
If I were to supercharge a Dell'orto carbed Lotus 912 low compression engine (as found in early Excel and Esprits) what would I need and how would I go about doing it?
Can't turbo it as found in the esprit as apparently in the Excel the heat sets fire to the engine bay.

[dtmpower]

Will you be putting the supercharger in front or behind the carb ?

[crofty1984]

Before the carb was my inital idea.
Make the airbox out of ally so it's a good bit stronger, leave the carbs where they are, then feed the output of the 'charger into the new, stronger airbox.
Though this is all just a thought experiment at the moment, so I'm willing to listen to all the options.

[davepoth]

First off, check whether dellortos respond well to being blown; they may not.

The most complicated bit of fitting a supercharger, assuming the fuelling isn't going to be a problem, is sorting out the belt run.

[GavinPearson]

It might be best to use the turbo esprit carbs, just find a supercharger that is the right size, come up with a supercharger mounting system, plumb in a charge air cooler and then send the pressurised air to the carbs.

That said, it may be cheaper and more reliable to use weber substitute throttle bodies.

[mad4amanda]

And remember superchargers also generate heat!

[tr7v8]

You'll need a supercharger like wot I have in my garage. A Vortec V5 G trim which I would part with, PM me!
Also PM me as I have a spreadsheet for calculating all the parameters, again PM me. I might add one is ot dependent on the other.

Assuming that lump runs around 10ish:1 CR then you'll only do 3-4PSI boost without an intercooler, which is not really worth the effort, but with an intercooler you'll probably manage 12-15PSI.

[marshalla]

davepoth said:

First off, check whether dellortos respond well to being blown; they may not.

They won't - but you might get decent results if you use later tri-jet version as fitted to the HC Excel SEs and Turbo Esprits. I'm not sure if they're identical in both applications, but the version on the Esprit can handle the boost pressure from the turbo.

Edited by marshalla on Tuesday 26th June 07:24

[crofty1984]

Thanks all,
TR7V8, I'll PM you once I'm home re the spreadsheet. Thanks for the offer

I'm still digging the car out of the bush which has become it's home over the last decade so I'm not buying parts yet, these first few weeks are going to be just assessing what the heck I've let myself in for! Plus another project I've got to get running again

I was thinking about 6-8psi should get it up to about 225bhp, up from the standard 160bhp, provided the standard internals can take it. But that's for next year. Right now I just want it running and road legal!

If anyone's interested: www.danslotusproject.blogspot.com

[marshalla]

crofty1984 said:

I was thinking about 6-8psi should get it up to about 225bhp, up from the standard 160bhp, provided the standard internals can take it. But that's for next year. Right now I just want it running and road legal!

You can get that out of a 912 without blowing it at all - a few simple mods to head & exhaust work wonders.

[crofty1984]

marshalla said:

You can get that out of a 912 without blowing it at all - a few simple mods to head & exhaust work wonders.

Really? Do tell...
All the tuning stuff I've seen has assumed the HC as a base engine. If I could get 200 and a bit bhp from an LC without changing its guts I'd be a very happy bunny.

[marshalla]

crofty1984 said:

Really? Do tell...
All the tuning stuff I've seen has assumed the HC as a base engine. If I could get 200 and a bit bhp from an LC without changing its guts I'd be a very happy bunny.

Have a word with Mike Taylor at Lotusbits - most of the engine internals are interchangeable so a LC can become a HC without too much effort - but you may well find that playing around with breathing and cams can achieve what you want : http://www.lotusbits.com/improving_your_lotus.pdf

[crofty1984]

That would be ideal. If I can avoid changine pistons, etc I'd rather do that. Plus I expect decent cams and breathing wouldn't hurt if I did decide to eventually upgrade to HC.