Compression Question

[lotusessex80]

Lotus 910 2174 cc four-cylinder in-line, 16-valve DOHC,

two Dellorto DHLA4OH side draugh carburettors.

Bore & Stroke: 95.25mm x 76.2mm. Compression: 7.5:1.

Block & Head: Aluminum alloy

Garrett AiResearch T3 Turbocharger running at 8psi

Power and Torque

210bhp @ 6250rpm

200lb ft @ 4500rpm

this is very low compression, but why is the turbo only pushing 8 psi? Is it because there is no intercooler to cool the turbo? or maybe because its a carburettor? please enlighten me. The reason why I ask is because i plan on buying a one soon but fuel injection, I think the fuel injection have higher compression. 210hp is good but I think the 910 can push 300hp no problem. Does the aluminum block have Iron sleeves?

[andydclements]

As the air intake temperature was relatively high it means the engine is likely to knock (pre-ignite) and damage pistons etc. By applying a charge cooler later on they were able to increase the boost without suffering pre-ignition.

Fuel injection can also help to control this by being more precise and more variable with the fuel delivery.

The liners in early cars were iron, but later swapped to aluminium with a ceramic coating, this proved to be less prone to bore wear.

Yes 300Hp is no problem, a lot more can be derived , but 300 is what's given in the late production cars, so Lotus must feel it's an achievable sustainable power level. You could probably get that with minor tweaks, filters, exhaust system and chip (possibly best to increase charge cooling as well).

[USAndretti42]

At the time, 210 bhp was plenty. The car was one of the quickest for the money so it didn't need anymore power. Increasing boost makes driveability worse by increasing the difference between off-boost and on-boost performance.

Also, more power at the flywheel means more heat to the water and oil putting a bigger strain on the cooling system.

Then the transmission has to cope with the extra torque and the Citroen-Maserati box in the Giugiaro cars was on its limit with the 210 or so engines.

Increasing engine output by almost 50% affects a lot more of the car than just the engine.