Olli Snellman

Most tracks here are short & curvy, so that's why i plan this mod. Of course original cooled LSD trans is still in my garage if needed.

Thom

I am temporarily dropping the idea of the 6 speed gearbox with taller gears, as for only an extra gear that will be used every once in a while costs are just too high.

This is what I would do, as revs climb quick enough with the torque from a 3.0 and anything shorter than the stock 951 gearing may be too short.

95ONE

I couldn't imaging shorter anything with 400rwhp. Drag tires barely keep the tires from ripping apart in 2nd. 1st gear is useless no matter what tire I use. 2nd to third is so sweet and almost feels like a perfect switch.. almost pulls harder into third. Im very happy with the stock gearing at this power level.

Diver944

I think that's a wise decision Thom. I certainly find that a 3L+ car has so much low down torque and power that the standard gearbox suddenly seems like a perfect close ratio box. You can be cruising in 5th at 70-80mph and if you suddenly need a shot of speed then a sharp press of the throttle has you right in the power band without needing to change down and highly illegal speeds are soon within your reach

If you fitted a higher ratio box to gain a higher top speed (why?) then you'd be back into the territory of slower response like a standard 2.5 car

Thom

Well, the 6 speed gearbox I have in mind would have nearly the same first 5 ratios as the 951 gearbox, so basically it would feel the same as the 951 gearbox in any of the first 5 gears.

The point of an extra, long 6th gear isn't more the potential 200mph top speed - which has little value outside of a pub - than the ability to combine cruising on motorways with improved fuel efficiency. Even with a pretty tall top gear I feel it would possible with 3.0+ engines like ours to cruise at 80mph at 2500rpm (which would be the case with this "ideal" gearbox) without them feeling any more sluggish than an entirely original 2.5.

Whenever I recently found myself deep into 100+ mph speeds (naturally on private roads) I felt the car's active security was far superior than with the 2.5, with which I felt slightly concerned when driving at such speeds as the engine lacked the extra responsiveness needed when everything around it is "processing" quickly, driver included.

This all leads me to believe that driving in 6th at 100mph with this custom 6 speed gearbox would overall feel the same as driving in 5th at 80mph with the stock gearbox, or at least not worse than with a stock 2.5 engine.

Robby

Hey Thom- congratulations!!! I just saw this thread, so I'm a month late. I do agree, completely, on your gearing thoughts- I just never had a strong enough 951 to confirm...

Thom

Quick update.

After several tries at improving the airbox+snorkel design it was replaced with a SFR Maf pipe and a cone filter in the usual location.

The stock 968 fuel pump was replaced with a Walbro GSL 392.

A Saïkou Michi oil catch can was installed.

The engine works great overall and I regularly see 17psi at 2700rpm.

For some reason the knock sensor remains quiet when running a peak boost of 19psi while it blinks erratically when running 17 or 18psi - ??

Tom M'Guinn

I am not familiar with sfr's fuel controller, but is there a chance you are running leaner at 17/18 creating the pinging, but jumping over to a richer part of the map at 19 to eliminate the knock?

marcoturbo

Thom runs a Vitesse MAF. The MAF pipe is the only SFR stuff he runs.

Chris White

The valve train in the 944 is pretty noisy - get the most knock counts when decelerating with no fuel begin injected!!

fast951

You are running 17psi and 19psi on pump gas?

Since you are running the V-FLEX software which is boost dependent. It appears that you need to run a different image than the one you are running now. Go to image #4 on your chip/board. See how it does.

I don't think running 17,18 or 19 psi is a good idea on pump gas. You are taking away the safety margins.

Thom

I monitor knock with a SciVision KnockView (a pretty effective device btw) as it lights up as soon as the knock sensor is stimulated.
When the KnockView lights constantly instead of just blinking I don't risk myself above 15psi and wait until I have to fill the tank again with fresher fuel.

The knock blinks are very short so this could mean something else may be making (inaudible) noise in the engine and it may not be actual knock.

I was just was surprised that the engine made "less noise" at 19psi than at 17/18psi.

theedge

Neat to listen to through the stereo via a knock sensor amplifier though.

Thom

"Houston, we have a problem..."

Since I have been regularly finding coolant in the oil catch can when driving under boost, this thread suggests the HG is on its way out.
Plugs look fine and compression numbers are excellent.

Finding coolant in the oil catch can wouldn't have bothered me much if a friend didn't bend rod #4 on his 2.5 because of a failed HG, though his engine showed no typical sign of HG failure.

Since my engine has never overheaten, I am now wondering what could have damaged the HG :
- Lean mixture? It's not what the logs suggest (apart from a tedious lean spike, but I'm not sure it can be related).
- Raceware headstuds (torqued once at 35/50/65/85) don't work with a stock headgasket?
- stock 968 headgasket doesn't work in a turbocharged application?

At this point I am considering just replacing the stock headgasket with another one and fit a LR steam vent kit, but if you guys have any suggestion on other things I should check/do, I'm all ears.

Duke

Are you sure it's coolant and not just condensed water?