Engine build progress

[George Elliott]

Thom, just a thought, can the ISV be a factor? dont know if you are open crank case breathing? just trying to think of something / some combination, which is common to other cars its usually something simple George

 

[TTM]

Tom, thanks for the feedback. I have a new fuel damper waiting for installation, it's the only "mechanical" part in the fuel delivery system that I haven't replaced. I took the car out for a spin yesterday evening and noticed that the lean spike is almost absent when flooring the throttle when vacuum is not at its highest - let's say you drive at a vacuum evel of -5psi (light throttle), flooring the throttle from there shows a decent evolution in the AFR and no brutal lean spike such as the one shown on the graph I posted. I would think the absence of lean spike as the throttle is more than marginally opened seems to go in line with your theory...? George, Thanks for the suggestion. Well we didn't test the ISV when building the engine, and the one used is virtually "new old stock" - along with the throttle body it came from an early '86 that had about 3k miles when it was crashed. For what it's worth we pressure-tested the intake at the entry of the intercooler several times and found no leak. Well well well...

 

[marcoturbo]

Do you Zeitronix logs now look lime mines ? At least, you drive like a guy now []

 

[TTM]

Just thought I would post a quick update, as I installed an oil catch can last week in order to dry up the air intake line. The engine works very well overall and I regularly see 17psi at 2700rpm. I have not identified the cause for the lean spike but noticed it was avoidable by opening the throttle progressively instead of just flooring it like a nutter. For some reason the knock sensor is totally quiet when running a peak boost of 19psi while it blinks erratically when running 17 or 18psi - Bizarre... How long do you chaps think Alusil bores will last if running such high boost? The rod ratio is higher on a 3.0 than on a 2.5 and I am a bit concerned with lateral loads between piston/cylinder...

 

[marcoturbo]

According to a well known seller, you should run lower boost than your current level...

 

[TTM]

Yes Mummy []

 

[Diver944]

Thom, we have guys over here that have been running boost levels in excess of 20psi for many years without major problems. I know that John at Vitesse warns not to run over 15psi unless using mega expensive race fuel but I'm always wondering that our 98RON Super Unleaded is actually better than the premium pump gas they have in the US. I know the Ron/Mon/Octane comparisons are not straight forward so its not easy to do a direct comparison The trouble is that in the US one can pick up 105 Octane race fuel for much less than we can get street fuel here in Europe, so most of the ultra boosters over there use that.

 

[333pg333]

...or E85. We pay about $5 per litre for race fuel 105oct. For E85 it's .99c p.l. and I've had my stock 2.5 motor hit over 2.1 bar with it. Don't think the headgaskets like that sort of pressure, but no sign of pinging or retardation. Still Thom, 17psi at 2700rpm is very good. What sort of size is your turbo?

 

[TTM]

In my experience, a healthy, original engine (turbo, IC, wastegate, etc) will hardly ever suffer from knock damage if it's run below 16psi with fresh fuel, so it makes sense to me John warns his customers not to run any higher boost. I personally wouldn't venture over that limit if I did not monitor (inaudible) knock. Patrick, I'm not sure about the turbo (only Simon at SPS will know in detail) but according to the compressor cover it looks like it's based on a GT30.

 

[marcoturbo]

Any update ? Any pic of your Belgium Mail firewall upgrade ? []

 

[TTM]

Sly said it was ok to post about his engine, so here's the bad news : rod #4 is bent. [&:] Probable cause is a turbo that was spilling too much oil into the intake, resulting in poor combustion. Other ideas? Now either the block will receive good rods or will be replaced with something "slightly exotic" based on a 968 engine. I vote for the latter, as the lack of positive stress related to doing any major work has made me feel slightly depressed in the last months. [>:] [] My engine is doing better every day, mileage is now up to 8700 miles, hardly uses any oil at all. Took apart the intake line to clean it from the usual oil film though, which I should have done anyway when I installed the oil catch can (me stupid). Considering having the hood modified with old school louvers to help extract air from the intercooler, which at this point I think won't be replaced with an aftermarket unit. I calculated that a SFR front mount intercooler would equate to about 9000 miles worth of fuel mixed with octane booster additive, so will probably go that way to avoid knock.

 

[TTM]

Update - and sorry if rehashing this engine stuff is becoming boring! Sly sourced a fresh 968 engine though what he will do with it is not decided yet. The lack of boost combined with driving an '84 NA Lemon Edition everyday means the priority is to have his turbo S running again as soon as possible, so the priority is to replace all rods on the 2.5 then drive it at 20psi until "something happens", hopefully not too long before his 3.xL will be complete. Apart from the same old lean spike my engine is doing well and it appears it will do a fair bit of miles before going pop, however other things on the car are becoming problematic - must fit softer front suspension springs and go for a less agressive geometry set up as the car has become rather unpleasant to drive. It doesn't inspire confidence. The steering feels like it's becoming heavier - could that be a sign of a failing steering? Differential bearings are becoming louder and induce minor but still unpleasant vibrations in the back of the car and in the seats, when on the overrun. Will take off the CS buckets and fit back the original seats to see if they help.

 

[DivineE]

Could all of those things be due to a failing LSD that is slipping and biting in a straight line? You can still buy and replace the plates if that's the case. Vibration like clutch judder: check Lack of confidence due to unpredictable handling: check Heavy steering: Can fight your steering especially around the straight ahead Might be fitting symptoms to suit a theory slightly but that's what first came into my mind when reading your post.

 

[333pg333]

What's your suspension Thom, and geometry? The stiffer springs shouldn't contribute to a heavier steering feel. There are lots of guys running 600lb/in + front springs so I don't believe that is your issue. I've had a couple of intermittent steering system issues of late and I can tell you that 275x18s up front are not so much fun with no p/s! I've forgotten what it's like to drive a fairly stock car with no creaks, bangs, whirrs, and groans that mine has but I'm so used to transmission / lsd noises in amongst the metal suspension bushings sounding like an old bed in a bordello. Are you intending for your car to be more of a stock looking wolf in sheep's clothing type of setup?

 

[barks944]

Heavier steering is definately a symptom of the double knuckle coupling between the steering wheel shaft and the steering rack. I replaced the one on my lux the other day and its much nicer now. You can also try some release agent on the joints, this is a temp fix and wont last long but it should last long enough for you to tell if the shaft is on the way out. Its easy to replace just involves dropping the cross member a little bit.

 

[TTM]

Before I got the turbo I did much thinking on transmission noises, rebuilt the torque tube on the S2, replaced the gearbox, had the clutch replaced, and over the years with the info I have gathered it seems differential bearings on 944 gearboxes will necessarily become noisy over 60k miles on standard cars. The gearbox on the turbo was replaced with a new unit just 60k miles ago but the torque tube is original at 180k miles. With the performance of the 3.0 engine I feel the transmission is suffering more than it did with the lightly modified 2.5 engine. I have a spare torque tube that I am going to rebuild for the turbo but considering what I experienced with the S2 several years before I am confident this noise on the overrun comes from the gearbox. At 180k miles the rubbers that interface the rear cross brace with the shell may have got super stiff by drying up and may not absorb drivetrain vibrations anymore. What do you think? Or perhaps it's only the gearbox mount that is shot. I have no evidence of it having ever been replaced. As for the suspension Pat the car has 3 way adjustable Moton Motorsport shocks at the front with I think 200lbs springs, which is not excessive, and basic Koni yellows at the back. Camber is -2° at all corners with a faire dose of toe-in, which is too much for a road car. Well I should say I liked it very much at the beginning as it suited the character of the rather peaky 2.5 very well, but with the turbo diesel-like performance display of the 3.0 these agressive geometry settings just feel "wrong" to me. I am trying to make a coherent, polished and refined package out this car that would suggest it was made by the factory as the new engine has really transformed its character and the way I drive it. It has gained a lot in performance but has lost a bit of its 951 soul. Perhaps I should have asked Simon at SPS to build a less efficient, more peaky turbo. Either this or I must find a solution to raise the boost above 16psi while make sure there won't be anymore knock. I am considering selling the Moton, that would come with a set of rebuilt JRZ rear shocks that I haven't installed, and fit a set of KW V3 that may perhaps help refine the whole package. I can't get anywhere 0° camber with the Moton because of how the struts are made. As genuine Motorsport items they are proving excessive for a road car. Tom, will look at the coupling, thanks for the suggestion.

 

[barks944]

Deutsch nine have said on rennlist that they have found a suspension system that is cheaper and better in all respects than the KW system. Might be worth chatting to them about that.

 

[TTM]

Tom, do you have a link? Been searching over RL for 30 min with no success.

 

[barks944]

He hasn't given any details yet, he just mentioned he was working on something... http://forums.rennlist.com/rennforums/7541466-post9.html

 

[DivineE]

Just for reference I went out in a 944t using Bilstein suspension the other day and the thing that struck me most was how comfortable it felt still. The shock absorbing over speed bumps and pot holes felt superb, softer than M030, but the car was running extremely low and still felt lovely and confidence inspiring in the bends. I wouldn't say it was a lot stiffer than M030 but with the hide height it worked very well.