DIFF Ratios...

[DR86]

I was just wondering if all of our City Turbos were running the same kind of diff ratio. My T2 needs 2500rpm to do the ton (100kph). Driving other cars, like a Corolla Seca needed more like 3000rpm, and so did a friends Skyline GTST, which needed 3000rpm.

Are they all the same???

[BOOSTBOY]

The difference between the city engine and most other small 4 cylinders is it's low reving nature.  Peak power is made at around 5500rpm where as corolla seca 4AGE will happily rev to near 8000.  That's why the cityT is geared so high... It makes alot of torque at low revs.

[DR86]

Oh yeah. Thanks mate. Hows the car going?

[Henry]

On the T11, max H.P. is 110 at 5500rpm. Max torque, 16.3 kg-m at 3000 which drops off gradually to 15kg-m at 5500rpm. then really drops.  Seems to me that is you change gears at an RPM that allows you to be above 3000 when you hit the higher gear (about 4500) then you will get the best without flogging it too much.  Mine does 110k at about 2900rpm. Anything over 5500 seems a waste of time.   Henry

[DR86]

Henry,

Mate, that is so true about the engine above 5500rpm. It's just so breathless and uninspiring. How i (or we) get rid of this 'strangle-effect'? Short of fitting a larger turbo though...

[Henry]

DR 86, you got part of the message, why do you need to go over 5500 anyway. Torque is what gives you the grunt, if it pulls like a train between 3000 & 5000rpm, manage your driving in that range, 5000 in second is about the open road limit, if you have spare engines to waste, send me one for safe-keeping. It's the intake and exhaust system that strangles it, may be done that way on purpose so it's harder to hurt. Like the VW principal, mount the carby on a 1 inch pipe about a foot from the intake valve and it will never generate enough revs to hurt itself. If these things reved to 7000 easily there probably would be none left for us to enjoy. Henry

[DR86]

5500rpm? What was i thinking? Redline is at 6000rpm... Sorry mate, my head was't screwed on propley when I replied.  :-[

So when does the uninspiring rpm range come in for my T2? At about 3500 and above... At about 2500-3500rpm, it feels like its gonna fly, then after 3500rpm, it justs stays flat and lifeless, not good for a 'roll-on' competition with my mates Skyline GTS's (there's a few of them).

Would you know how much it is to rebuild a T2 engine, Henry? To stock specification that is? I think I need new valves (inlet and exhaust), as my donk has done over 600 000km. Or, would it be cheaper to just simply buy a imported engine and fit that? As it would come with a fresher turbo and valve-train, would it be more logical?

Any sugestions would be greatly appreciated.

Cheers!

[Henry]

DR86 sounds like it's not breathing properly, if it was wear causing that sort of power loss you wouldn't see the thing for smoke!! Check your air filter for flow and the turbo outlet hoses and intercooler for leaks and the fuel pressure. A compression check will tell you how worn it is, should be 9.5kg/cm2 at 300rpm. If it's down much on that, squirt a bit of oil in the cylinder and re-check, if it increases it's the rings, if it doesn't it's the valves. Spark timing could also be a cause, your vacuum advance canister is probably stuffed but it should still rev rairly well. About 18 months ago there was one rebuilt in Adelaide for about $1000 without the head. Hope that helps. Henry