Engine build progress
- Thread starter TTM
- Start date
Indeed K27 coldside with K26/8 250 turbo hotside 360 thrust bearing, old technology, but flows lots - Was on the car before Mr Peckham owned a 944 - If I had met him sooner it would be spooling much earlier! Oh and its still on there, car is untouched still, will hopefully get some time with it over the next couple of weeks, Tony
TTM
Well-known member
I switched to E85 today. The throttle response has improved, the car now is nearly as responsive off boost as it was on unleaded with the original intercooler. The engine is even quieter than before, feels like it's running more smoothly, especially under full load. I didn't dare turn the boost above 15psi though, as even though the big intercooler provides fresher air to the engine, I know that detonation happens only once when running E85... [&:] There is still that little bit of lag due to the turbo having to fill up the bigger intercooler, but my hopes of getting back the stunning drivability and response pre intercooler upgrade are now on a bigger exhaust.
DivineE
New member
Have you been following the talk about methanol on the rennlist? The fact the guy dyno'd 358hp on regular unleaded and then 414 with his methanol suddenly makes it very plausable and very interesting for me to consider as something for a track day, drag strip or even just a good drive.
Thom, what changes have you made with the software to run E85? Have you any control over timing? Even though you may get less warning of detonation with E85 you have a lot larger margin to work with. I have run over 2bar when a vacuum tube worked lose. I know Sid has used 35psi on his car. Not saying you should go crazy and cut loose, but you should also be able to 'profit' from the switch. You can run way over 15psi provided you have everything sorted. Especially on the street.
TTM
Well-known member
With regards to the software I just switched to the second E85 map (+35% fuel) on the Vitesse chipboard and did a new fuel map with the Piggyback. The Vitesse E85 map are supposedly way more agressive on the ignition side so I know I am taking advantage of this already. I am getting excited at the idea of running 18+psi but I'm not sure the stock 968 headgasket will like this for long. I also ignore the lambda value of the "E85" I filled the tank with, maybe it's E90 or E70, so I also have to keep a safety margin there.
With my old pre VFlex setup we had to add a hell of a lot more fuel in the Fuel tables, but with the Vflex it has 'images' with this added already. Sounds like Thom has gone for the 'doctor' straight up. We went up in stages before trying the aggressive map. It eventually netted 50hp at the wheels extra with a clean up so that is great that you can get this at the flick of a switch. As for the stock h/gasket. I think on the road this should hold up to 18psi comfortably. Probably more. Not sure ultimately what gasket would hold for longer, 2.5 or 3L with siamesed bores, but either way you should be ok easily to 18psi IMHO. After that we ran into restrictions with some other part of the motor as far as flow goes. Probably stock head, intake, throttle body, headers etc....it never ends...[
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TTM
Well-known member
I used Raceware head studs, which instruction sheet reads tightening 35/50/65 lbs.ft, then do a heat cycle and retighten to 65/ lbs.ft. Naturally I didn't like the idea of having to take off the cam tower and redo the T-belt just to check the torque, so we tighened them to 35/50/65/85 lbs.ft with no retorque. Now I am concerned that this is too much torque for the stock headgasket to handle, that it has "fragilised" it and that running too much boost may blow it. That said, if I feel it's going to blow one of these days, then perhaps I may as well do things in style by increasing the boost until it blows up - by then there won't be any more doubt
Just have a Cometic gasket handy for that day Thom. [] There also seems to be some conjecture over what headstuds, what torque, what tightening sequence, what gaskets, what to do with gasket...blah blah blah. The big advantage of the Cometics are that if you do spring a leak at high boost / on the track, you can just turn the boost down and drive home. Hell, we even did a dyno run with the gasket in this situation. You just have to watch the coolant moving across to the overflow bottle and pull back.
] There also seems to be some conjecture over what headstuds, what torque, what tightening sequence, what gaskets, what to do with gasket...blah blah blah. The big advantage of the Cometics are that if you do spring a leak at high boost / on the track, you can just turn the boost down and drive home. Hell, we even did a dyno run with the gasket in this situation. You just have to watch the coolant moving across to the overflow bottle and pull back.
TTM
Well-known member
So I did a first drive this evening at 18psi with E85. On the plus side, the performance is just surreal. I had tried 18psi when I was running unleaded, but the difference with E85 is very noticeable, the engine is far more agressive and rev-hungry in the upper ranges. Traction is still surprinsingly good, at least from 3rd gear on. It's just marvellous, I am eventually touching the level of killer performance I was aiming at with the 3.0 [] On the negative side, while I was on the way home I tried a last full throttle action in second gear and suddenly heard a "POP". It sounded like a coupler between the turbo and throttle body had popped, but the engine still worked fine, it didn't feel like it was a vaccum leak. I made it home slowly with my eyes held on all gauges showing nothing particular and after I cut down the engine I noticed the coolant level in the tank was a fair bit lower than it should. I checked the overflow hose that was very wet indeed. So the sound was the coolant tank cap that couldn't put up with the pressure in the coolant circuit -> the headgasket is definitely on its way out! [8|]
] On the negative side, while I was on the way home I tried a last full throttle action in second gear and suddenly heard a "POP". It sounded like a coupler between the turbo and throttle body had popped, but the engine still worked fine, it didn't feel like it was a vaccum leak. I made it home slowly with my eyes held on all gauges showing nothing particular and after I cut down the engine I noticed the coolant level in the tank was a fair bit lower than it should. I checked the overflow hose that was very wet indeed. So the sound was the coolant tank cap that couldn't put up with the pressure in the coolant circuit -> the headgasket is definitely on its way out! [8|]
sawood12
New member
With the only apparent disadvantage of E85/biofuels causing you to stop more frequently at petrol stations for a fill up, wouldn't a more elegant solution for those short sharp bursts of extreme speed be to run lower boost pressures (thereby preserving the engine and transmission) and using NOS?
DivineE
New member
I've never liked NOS, it doesn't seem like 'real' power to me as you only get it in a few second bursts. Something like a high octane fuel lifts the performance of the car for a whole tank. I also hear its very hard to accurately account for in the mapping, but that's just what I heard.
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