Engine build progress

[George Elliott]

Thom, this is a great thread and you deserve all credit for what you have achieved with this engine build. I dont have a monster engine, but my 2.5 with Simon's re-engineering has provided me with a spectacular demo of what a 951 can be. You perhaps have what a 968Turbo could have been....well done and thanks for keeping us posted. My car had 1,900 miles on when I first test-drove it, I would say the engine felt slightly tight mechanically, and now with 5,200miles it is a little less tight. I regard the first 10,000 miles as running in and I only go beyond 5500rpm when up to full operating temp' and in exceptional circumstances. Good luck with it George

 

[TTM]

Chaps, thanks for the kind comments. Mileage now is up to 1,200 miles and I use it pretty much everyday (have been on holidays since start up). At 14psi the butt dyno suggests it is already as fast as was my 2.5 at 18psi, with the added benefit of showing little to no lag, though boost is not really needed in real world driving on country roads as the engine feels as responsive as my S2, even with the taller gearing of the turbo and I haven't even found myself yet wanting to floor the throttle for a reason other than checking the AFR under wide open throttle. All of this with an unmodified snorkel. I must say I found myself looking for an extra gear when driving on the Autobahn - the revs build so quickly under boost in fifth gear it's almost ridiculous. Fitting a gearbox from a 968 turbo S would appear to be the next step to complete the package properly, though it would probably cost half the engine [8|] Surprisingly MPG is as good as with the 2.5 - getting between 25 and 30mpg depending on the roads. Again, the added torque in low revs and responsiveness means it doesn't need or pushes you to get on boost to get moving quickly. Sound-wise I am also well-pleased with the full '86 exhaust line. You can hear there is more cavalry under the hood than with a 2.5, and it makes a relatively lively yet reasonably quiet rumble. Scott, Am looking for places around here which could be worth a visit to you British folks. Combining a trip with a trackday at the Rheinring and/or 924/944/968 meet and/or a dyno test in Germany and/or a visit in the new Porsche museum might be worth a trip. George, You certainy have one of the best 944 around. I wish I had the patience of Simon and get mine stripped down for a full respray, as its looks aren't worthy of its engine! Enjoy it!

 

[satancom]

Sound-wise I am also well-pleased with the full '86 exhaust line. You can hear there is more cavalry under the hood than with a 2.5, and it makes a relatively lively yet reasonably quiet rumble,

Great thread Rebuilding an engine is a great feeling, only surpased by hearing it burst into life for the first time Not a Porsche but the first startup of an engine I built out of parts in my spare bedroom.. The misses was happy to film as it was finally out of the house http://www.youtube.com/watch?v=hKClQYabCxo

 

[JarmoL]

ORIGINAL: TTM I must say I found myself looking for an extra gear when driving on the Autobahn - the revs build so quickly under boost in fifth gear it's almost ridiculous. Fitting a gearbox from a 968 turbo S would appear to be the next step to complete the package properly, though it would probably cost half the engine [8|]

Hi there Thom, Well done with the engine build.. I wish you many trouble free miles with it.[] You can have little help for the short gearing issue by installing S2's fifth gear set. I have this set up in my transmission (951S gearbox). It will lower engine revs about 200-250 rpm compared to original 951S gearing. Of course 6 spd with proper gearing would be ultimate solution but it's very expensive as you said. I have a 2.8 stroker engine in my 968 and the bigger gap from 4th to 5th is not a problem in normal driving. Luckily our race tracks are so slow I don't need to use the 5th at all. [] Jarmo

 

[Diver944]

Sounding good all the way Thom, I have found the exact same thing with the gear ratios. The extra capacity and power of a 3.0L+ makes it feel like you have a very short ratio box, when in reality it is the same 944T unit that feels quite widely spaced in a standard car. Normal driving in mine returns roughly the same fuel consumption as it did before, but when driven very hard on track the extra fuel pump and big injectors can empty the tank in around 150miles []

 

[TTM]

Mileage is now up to 1,700 miles [] Though the coolant temp and oil pressure are where they should be I really don't like how quickly the engine warms up - it seems to really dislike idling under the sun (we have had no less than 35°C in the shade everyday since last week). As I posted earlier it warms up as quickly as my S2, if not more quickly, and much much quicker than the 2.5, and though it seems normal I just can't get to grip with it yet. I will feel better when that bl**dy hot summer will be away [8D]

ORIGINAL: JarmoL You can have little help for the short gearing issue by installing S2's fifth gear set. I have this set up in my transmission (951S gearbox). It will lower engine revs about 200-250 rpm compared to original 951S gearing. Of course 6 spd with proper gearing would be ultimate solution but it's very expensive as you said.

JarmoL, I was recently told about some Audi 6 speed gearbox that had the same ratios as the 968 turbo's, will have to look into it further. The S2 fifth gear set is indeed longer than the turbo's... Hmmm food for thought [8|] Paul, Pleased to hear you have the same "issue". It sorts of suggests my car is not too slow either [] satancom, Hmm... The link to your video seems broken?

 

[TTM]

ORIGINAL: TTM And now poor Sly has got a problem with his turbo... More on all this later.

Time for an update on Sly's car. The last time we took apart the airbox and IC ducts we found decent amounts of oil, there was almost a pool of oil at the the bottom of the airbox! Sly has been running 20psi of boost in the last thousand miles and has been pretty pleased with it - this is the type of boost pressure the LR75 seems happy with - he dialed the fueling until the KnockView showed no knock (which got him to an AFR of 10.5 under full load) but noticed since that boost systematically fell down to 14psi in upper revs, along with a worrying screeching noise coming from the front left side of the car. Was that the bearings from the turbo giving up the ghost?? Ahem... [&:] Today he took the airbox apart again and noticed that the section of the snorkel mating with the airbox had collapsed, necessarily caused by the vacuum caused by the turbo under full load! The section of the airbox mating with the snorkel features two vertical plastic strengthenings that prevents it from collapsing, but the snorkel doesn't. He then drove the car without the snorkel and the problem disappeared - 20psi until redline, no more screeching noise. I believe I will have the same issue once my engine is run-in and the boost raised, and the double-intake snorkel that we made for my car is unlikey to prove a proper solution. Time for some proper modifications and stop ham-fisted engineering []

 

[Diver944]

That's a very interesting occurance and show's just how much 'suction' the large capacity engines and bigger turbos create through that tiny snorkel. We had to remove the airbox and snorkel on my car shortly after running in because the vacumn was so great that it would literally suck oil straight through the breather system attached to the airbox. With a MAF and 3" pipe leading to a cone filter this problem disappeared immediately and stopped me worrying about a huge oil consumption issue I do like the stealth appearance of a standard airbox so will closely watch your experiments with modified snorkels []. Is it possible to ovalise the intercooler pipe below the snorkel, thus allowing more space for a bigger snorkel?

 

[George Elliott]

Thom, similar suggestion to Pauls, but mod the bonnet. A discrete bulge on the bonnet would accomodate the full round bore you need to get cool air from under the front wing. (assuming there is enough in there...!!) Its amazing that the engine / turbo vacuum is capable of collapsing the duct. Perhaps that explains why the 968 turbo intake did not source air under the wing. George 944t

 

[TTM]

Yes Paul, I vividly remember you saying this in another thread. Ovalising the IC pipe is a sound idea. I feel stupid for not thinking about it earlier... Will try to find a used unit and work on it. In an ideal world one would be able to lower the MAF/J boot assembly thus make some room to lower the IC duct, but on a car still running air conditioning this may be mission impossible. George, modifying the bonnet would require skills we sadly don't have and we don't feel brave enough yet to butcher a bonnet! I saw a modified German 944 turbo using NACA ducts similar to the 968 TS but noticed the intake on the left side, for the airbox, came just in line with the headlight, and the car I'm refering to had a 924 CGTS headlight conversion. I'm pretty sure it wouldn't work well with raised pop up headlights. I think it would also be an issue in the rain, though one may not want to use full boost in the wet [] I recently saw another original 968 TS and even though the NACA duct on the hood is a better solution than the snorkel I'm sure it can be improved. By the way George, is your car still running an orginal snorkel or did Simon make something special to accomodate the turbo he fitted? I assume this turbo would suck a lot more air than an original K26? At this point running the airbox without the snorkel seems the easiest way to avoid the issue, at the cost of sucking in hot air. The double intake snorkel we made for my car is made possible by the lack of air conditioning (there is room thanks to the absence of the AC bottle usually attached to the left side of the left front member) as we routed an additionnal duct from the bumper, but it still attaches to the snorkel before the fundamental restriction just over the IC duct. Since we fitted it I can hear the turbo spool but it doesn't seem to make any other difference with an unmodified snorkel.

 

[George Elliott]

Thom, Yes, my car has the standard snorkel and the standard restrictive IC, downpipe etc. Its fine for daily use, but I do wonder what it would be like if....... No - its great as it is. Keep up the good work George 944T 964

 

[TTM]

Mileage is now up to 3k miles as I've been using the car to go to work for the last couple of weeks. Oil consumption is still nil. I took apart the intake up to the turbo to check for layers of oil and did not find anything worrying. Even with the double-intake snorkel the turbo feels like it doesn't build pressure as quickly as it should - logs have shown it won't reach 14psi of boost before 3200rpm. How good/bad does that sound to you? I drove the car without the snorkel (haven't done logs though) and it seems to build boost a bit earlier but I noticed "light" (inaudible) knock, probably due to sucking hot air into the airbox. I will still keep relatively gentle on the engine until it will have done 6k miles anyway, by then it should feel mostly run-in. It's already plenty fast and doesn't really need to be any faster than that, at least for road driving.

 

[Diver944]

14psi by 3200rpm sounds pretty good through the snorkel, but I suppose it depends if your turbo is specced for quick spooling or ultimate top end power. Here's a log of mine for comparison. The red line was with the AFM, snorkel and a manual black knob boost controller, it reaches 14psi by just about 2900rpm. The black line was with the MAF, a cone filter and a Greddy boost controller and is slightly slower at 3000rpm but I had it tuned a bit richer for safety. The AFM setup was at a lean 12:1 AFR which will make it spool quicker because it's hotter and the MAF setup was at 11:1

 

[dann944]

blimey, whats the 0-60 on your car Paul?

 

[sawood12]

ORIGINAL: TTM Mileage is now up to 3k miles as I've been using the car to go to work for the last couple of weeks. Oil consumption is still nil. I took apart the intake up to the turbo to check for layers of oil and did not find anything worrying. Even with the double-intake snorkel the turbo feels like it doesn't build pressure as quickly as it should - logs have shown it won't reach 14psi of boost before 3200rpm. How good/bad does that sound to you? I drove the car without the snorkel (haven't done logs though) and it seems to build boost a bit earlier but I noticed "light" (inaudible) knock, probably due to sucking hot air into the airbox. I will still keep relatively gentle on the engine until it will have done 6k miles anyway, by then it should feel mostly run-in. It's already plenty fast and doesn't really need to be any faster than that, at least for road driving.

You may find that a double snorkel solves the problem. If you relieve the restriction then you wont see as much pressure drop across the airbox. I'm convined if you can get enough supply of air into it then retaining the airbox is best.

 

[TTM]

Paul, thanks for the feedback. With an extra 200cc, bigger valves and a cone filter, it seems fairly normal yours builds boost earlier than mine. My turbo was specced for mid range performance and it offers a good compromise between quick spool and uprange oomph. I don't know about your turbo, was it specced for quick spool or ultimate top end? Scott, yes I hope a properly-made double intake snorkel will work out well on my engine.

 

[TTM]

A quick update. The engine now has done about 3500 miles, still doesn't drink any oil, works fine, etc. I raised the max boost pressure to 16psi. I am beginning to have mixed feelings on how the car drives as it's not as exhilarating as it was with the 2.5 even though it quickly goes a fair bit faster. It requires being driven about 20 to 30 mph quicker than with the 2.5 for me to reach the same level of concentration, meaning it's a really easier and far more efficient drive than it was with the 2.5, at the cost of having to take more risks to feel the fun. The butt dyno suggests the 500Nm bar is reached and passed, but the very tractor-esque, linear torque delivery and the relative lack of extra punch up in the rev range suggest the bhp may not be up to even the 350 figure. A more aggressive camshaft may help there. I have been running it with the ignition set -2° as I noticed light knock under WOT, but with the original intercooler, airbox and a half-finished optimised snorkel I shouldn't have expected no knock at all. On the side of annoying things the gearbox has begun to make itself heard. With the 2.5 the transmission always was surprisingly quiet with regards to 944 transmission noise standards, and I suspect the new clutch to be responsible for this - I noticed the same thing when I had the clutch replaced on the S2 some years ago. I am also considering an alternative gearbox with longer gears to comply with the torque of the engine. It should take form as a 968 gearbox with the four last gears from an Audi gearbox. Will have about the same first 5 ratios as the 951 gears, with an extra 6th to reach an insane 205 mph the engine feels like it wants to offer me The problem is the 4 gearsets cost new almost the same as a custom SPS turbo, and the availability of used gearboxes is scarce as it was originally fitted to a third-world spec Audi. Also have to factor the costs for the rebuild of a 968 gearbox, the extra bits needed to fit the thing on a 944 turbo, resulting in a pretty hefty bill for "only" an extra gear. Food for thought...

 

[marcoturbo]

An AWS gearbox should be cheaper ! So you're telling you've installed a V8 engine in your car []

 

[TTM]

An ASW gearbox or any other S2 gearbox (with the 3.778 R&P) would be rubbish on a 3.0 as ratios would be way too short, though it might prove a useful mod on something as slow as your 2.5 []

ORIGINAL: TTM I am beginning to have mixed feelings on how the car drives as it's not as exhilarating as it was with the 2.5 even though it quickly goes a fair bit faster.

I took off the snorkel again yesterday, keeping the additional air line from the bumper and oooooo now it's a totally different kettle of fish [] Spool up is much quicker and boost peaked 1psi higher than before, without even touching the boost controller.

 

[TTM]

There is a problem with the car, that has been present since it was first fired up, that we cannot solve. Whenever the engine, warmed up, is left idling more than a couple of minutes, there is white smoke coming out of the exhaust and the strong unpleasant smell that goes with coolant being burned somewhere. Though there is no mayonnaise in the coolant tank and there was no trace of coolant in engine oil when I replaced it last weekend, it can happen to consume a little bit of coolant, but it won't consume any at all if I hardly ever let the car idle. The white smoke disappears as soon as I get on the throttle. Coolant temp behaviour is normal, as are all other important figures (oil pressure, AFR, knock, EGT) and the car really flies [] I checked all hoses and there is no leak. I have a couple of ideas of what could be causing this, but some suggestions from here would be greatly appreciated.