924Board.org

[stevekat]

I have swapped my Euro DITC box in and out with my U.S. box about 3 or 4 times. I'll go into more detail in a later post if necessary, but a quick summary.

Euro box has better low end and midrange response and acceleration, under partial boost or no boost. Car is much more responsive in low end, particularly starting from a stop - very noticeable. Assume it is due to more advance.

Trade off, is that on my car with CGT intercooler, and about 85 degree ambient temp, I have to limit max boost to about 11psi, maybe a tad less. Car seems faster with Euro box, overall, and much more fun to drive around.

With the U.S. box, car is slower and less responsive off a start, however recovers in mid-range when under mild boost or no boost (using boost in this instance as adding positive pressure to normal vacuum, not just boost over 0psi.)

With U.S. box, on my setup with CGT intercooler, I can boost up to 14psi or a tad greater without pinging, but this does not necessary result in a greater overall faster car - though maybe in some circumstances. The differences between the two boxes are really a trade off.

The trade off seems to be greater advance vs. greater boost. I am running 93 octane east coast fuel. After several tests, I have left the Euro box in the car, set on the lower 11psi max boost at around 85 degrees F ambient temp. The car is more fun in this configuration. I like the responsiveness on low rev, low boost, tooling around town. And have plenty of power on increasing and higher boost.

I have tried the Euro box with the timing retard connector undone. The car drives as well or better than the U.S. box. I would like to find out if this connector retards the timing consistently across the rpm and manifold pressure parameter range. When disconnecting this connector with the U.S. box, the car is very hesitant.

BTW, with the Euro box, the car in 5th gear below 3000rpm, even as low as perhaps 2400rpm, is pretty responsive. It doesn't chug much and one doesn't feel they are pushing the engine too much at this low rpm if they use care. With the U.S. box, I usually feel I am in some no-mans land between 4th and 5th gear. Fourth seems like the car is running at uncomfortably high revs for prolonged periods of highway cruising, while in fifth gear there is a little chugging (barely perceptible) and the feeling that the rpm are a few hundred away from the power band and that one cannot accelerate reasonably - resulting in lots of 5th to 4th downshift.

Beyond the 11psi max boost at about 85 degree ambient temperature with the Euro box, pinging incurs on wide open throttle and max load. From past experience, I have found one has to be cognizant of protecting the engine at WOT, max load, primarily if one gets to the track - lots of folks on the board run higher, almost insane amounts of boost with reasonably unmodified engines, and this is provisionally OK on the street if one doesn't do WOT, high load acceleration frequently or for prolonged acceleration periods, though it is risky. One can get lucky and hold their engine together for a long period of time with proper restraint.

But the folks that run 15 or 17psi, with or without intercooler, with few other mods, would melt down their engine in a lap or two on the track. Just wanted to clearly point this out to the guys that successfully run high boost on the street. Big difference between heat/ping circumstances at WOT/high load on the track vs. sporadic acceleration on the street.
_________________
"Never get out of the boat. Absolutely goddamn right. Unless you are goin' all the way."

Gone to new home: '81 924T, US version, CGT Intercooler, UTCIS-PT, Euro DITC, Greddy Trust MBC, Forged Fuchs Flat Dish 6's, Factory Recaro's.

[morghen]

great report!
when i drove my car on the track i always kept it in a superior gear just to keep the revs down.
reasons.....keeping traction(was a mostly second gear track)...preserving engine and somehow staying around max torque.

so..the US gas is inferior after all...i even drove the car with some 95 OCT in the summer without problems(they didnt have 98 there and i was nearly out)
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Supercharger and EFI kits
https://www.the924.com

[Khal]

[morghen]

[gegge]

Great stuff! That´s what I was looking for , any difference in the revlimiter?

Since the euro 931 was built for leaded 98 octan gas and 9 psi I have to say that driving with 93 octan @ 11psi even with an intercooler is fairly high. Guessing that the ignition curve is rather conservative then.

Would be interesting to know that the GT DITC does for performance..?
_________________
Carl Fredrik Torkildsen

924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs

[Rich H]

US ratings and RoW ratings for fuel are different.
I think 93 = 98 RON There was an explanation somewhere...

I run mine on 95 RON and I'm not 100% happy about it, thinking of going for expensive stuff but it's 10p a litre more expensive.... Might disconnec tthe retard line and see what happens...
_________________
1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

[Rich H]

( RON Octane Rating x 0.95 = AKI Octane Rating )
98 RON Octane x 0.95 = 93.1 AKI Octane (US measure)
100 RON Octane x 0.95 = 95 AKI Octane (US measure)

It's off the internet so must be true....
_________________
1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

[gegge]

Scary 11psi is the limit with intercoler..?

But I guess that you are right, I have read that too somewhere.
_________________
Carl Fredrik Torkildsen

924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs

[stevekat]

I tend to run about 11PSI due to two factors...one is the intercooler, the other is the UTCIS-PT that gives one greater control and flexibility of fuel delivery.
_________________
"Never get out of the boat. Absolutely goddamn right. Unless you are goin' all the way."

Gone to new home: '81 924T, US version, CGT Intercooler, UTCIS-PT, Euro DITC, Greddy Trust MBC, Forged Fuchs Flat Dish 6's, Factory Recaro's.