Modifying/Improving the 924 Turbo

[nicksonmsport]

as much as i would love to build a 924t engine like yours wes, i have decided im going to go down the conversion route, with something that has the sort of power im after without having to do lots of custom engine work etc.

so im going to concentrate on getting the shell rolling and then decide what engine to drop into the car

so if anyone wants a 924 turbo engine, i have a complete conversion available for sale, see for sale threads for details.

will be watching this with interest and look forward to seeing how this engine performs and the sort of power it makes!

[Wes]

Finally back on with my project.

Start of 3 inch downpipe/exhaust:-

[Wes]

Twinscroll twin gate manifold with EGT ports:-

[Wes]

Inlet manifold is the next thing on the list. In fact the whole intake system is to be finished next including charge cooler:-

[russmw]

Cracking bit of engineering with this build, the exhaust manifold looks like some form of modern art. My only concern would be the heat from the turbo and the closeness of the cam belt, two things that aren't going to get along well together.

Looking forward to more updates.

[nicksonmsport]

Good to see some progress wes. I'm really looking forward to the results! I am still undecided on engine choice for my build, yours may sway me one way or the other lol!

I'm hoping to have my shell fab work done soon enough, and I have most of the parts now to get it rolling too. So hopefully it will start to come together!

[Wes]

My only concern would be the heat from the turbo and the closeness of the cam belt, two things that aren't going to get along well together.

Don't worry, there will be heatshields and probably a turbine housing jacket going on.
The downpipe also needs wrapping as it will be close to the headlight.

[Wes]

I am still undecided on engine choice for my build, yours may sway me one way or the other lol!

I'm sure whichever you go for will be fine and make plenty of power.

I'm stubborn and have an affinity with the old 2.0L 8valve. I like it's simplicity and strength. The few weaknesses are easy to sort out.

There's a dutch guy who turbo'd the 9.3cr normally aspirated 924 engine and used standalone VEMS. I think the turbo was a GT30.
The engine was high mileage and stock apart from new headgasket, better cam and solid followers.

The engine only broke a conrod after shoving more than 2bars boost through with E85 and using silly amounts of advance whilst revving beyond 7000rpm just after a gearshift.

The heavy stock rods and massive peak cylinder pressure with high boost/E85/advance didn't work out well lol, but he said it was fast while it lasted.

With a rev limit of 6500rpm and pump fuel with sensible advance, they will take a battering.

You can easily remove the doubt though with forged Omega pistons and some lighter aftermarket rods.
Rev limit can be upped to 7200rpm then which is all you need with an 8 valve turbo.
Higher is fine but follower bores in the head will wear quicker apparently.

[Carrera RSR]

Just found this thread again. Last time I posted 2 years ago I had just refitted the head and got the Zeitronix datalogging set up. Since then it's been tuned, fettled, boost turned up, added a boost solonoid switch which limits the onset of fuel enrichment when boost is first applied, essentially leaning of the mid range until 4800rpm when full boost triggers the WUR to full fuel enrichment, tweaked ignition curve, added more boost, adjusted the 3.5" off turbo tapering to 2.5" at the rear end exhaust system, fettled some more. Mid fettling we did two power runs on a 924 dyno day last year. At stock 0.7bar boost it gave 175bhp. At 1.0bar it gave 225bhp, 20bhp short of a Carrera GTS. It now runs circa 1.2bar due to further tweaks but fear the turbo is now at or more likely beyond its efficiency. Oh how I wish I fitted the 944 turbo 250 compressor wheel when I had the chance. I believe the power gap to a GTS would be negligible which a larger compressor.

Engine bay looks like this


Cockpit with Zeitronix data display and Phormula KS4 knock warning

[Wes]

Das ist wunderbar

What's your lowest boost threshold for full boost Steve? (In any gear).

[Carrera RSR]

Das ist wunderbar

What's your lowest boost threshold for full boost Steve? (In any gear).

In 2nd and 3rd the rpm's rise far faster so its circa 3000-3300rpm and most certainly before 3500rpm to achieve 1.2-3 bar (far lower rpm if I were to run say stock 0.7bar). In 4th and 5th the rpm rise is slower and therefore boost builds in relative terms more quickly so its sub 2800-2900rpm. But the full boost threshold is subject to the cam being advanced or neutral, I don't retard as I want early rpm boost not at the top end. I had it advanced before I played with the fueling and timing. I pulled it back to neutral when I was fettling again. I haven't advanced the cam back again to bring boost on earlier. Ideally a day on the dyno would see the cam, fuel, timing and max boost fully optimised.

[woolie]

Great thread

[Carrera RSR]

How it sounds now.

PS Stock 924 turbo recirculating valve, not added dump valve. Just 1.1+ bar trying to find a way out of the intake system.

[944 Man]

I know someone who knows more about 924s than all of you put together and he has forgotten more about competition preparation than I ever knew...

I can direct him towards this post, if you like?

[Carrera RSR]

I know someone who knows more about 924s than all of you put together and he has forgotten more about competition preparation than I ever knew...

I can direct him towards this post, if you like?

Yes please Simon. As long as it's not Wodger