Boosting the turbo, is it wise?

[meharijames]

Ladies and Gentlemen,

I'm a very happy owner of an 88 esprit Turbo with Bosch K jettronic injection.

The engine has been rebuilt recently with 'racing pistons and o-rings' if that makes sense.
I would like to boost the turbo but can not find any mention of it on the board, certainly no recomendations.
Any advise would be greatful.

I fear it is a bad idea.

Thank you

James

[lotusguy]

meharijames said:

Ladies and Gentlemen, I'm a very happy owner of an 88 esprit Turbo with Bosch K jettronic injection. The engine has been rebuilt recently with 'racing pistons and o-rings' if that makes sense. I would like to boost the turbo but can not find any mention of it on the board, certainly no recomendations. Any advise would be greatful. I fear it is a bad idea. Thank you James

James,

The wastegate can be shimmed or a new spring added to open at a higher pressure, thus creating more boost. I have done this to my '85 Turbo and am running 10PSI vs. the stock 7.5PSI. I did this over two years ago and 10k mi. later, the car shows no ill effects, but I am constantly monitoring both the spark plugs for color and engine compression.

Without intercooling (chargecooling in Lotus Parlance), it's not safe to exceed 10PSI as you risk detonation which will very quickly destroy an engine.

That having been said, my increase in boost was accompanied by re-jetting (richening) my carbs to insure that it doesn't go lean under high boost as well as a switch to a cooler plug. I already previously burned premium fuel, but would have had to make the switch if I hadn't.

Your '88 has the advantage of having the HC engine w/ it's nikisil liners. But, the Bosche k-jetronic isn't as easily modified to increase the fuel available to the engine as my Dellortos were. You will almost definitely need to swap out the injectors for higher flowing ones, but there's still the issue of properly metering it when required.

On my carb'd car, this is accomplished with the fuel regulator which increases the fuel pressure, and correspondingly volume, in accord with higher boost. Your car lacks this simple solution and so you're probably looking at modifying the Bosche's rudamentary (as compared with today's truly dynamic ECUs) computer. This is hard wired ROM, so it isn't easily done. I'm sure if you search, you can find a firm which can do this, but I doubt it will be cheap. It isn't a matter of simply snapping in a new chip.

Then there is the limiting factor of the Citroen C-35 gearbox, so while it certainly would be possible, I think you'd find it cost prohibitive, especially when the increase in power would be limited by the factors I've mentioned. Happy Motoring! ...Jim '85TE

[meharijames]

Jim,

What would we do without you?

Thank you again.

I think it is all a little too difficult for what will be little gain.

My workmates think it is very funny as all they do is buy a $50.00 boost control valve and 2 clamps.. Never mind, they also have a hadbit of blowing up their japanese engines.

I've forwarded your response to my mechanic.

Again thank you

James