Friday, February 06, 2009 - 10:11 pm, by: Simon Martin(Commander)
Low milage soarer engine in my Cressida (5spd), leaking across the water jacket, blasted the entire contents out the overflow tank, and i don't have a working temp gauge so it overheated...(yes I know i should have had a working temp gauge etc. etc. told you so, blah blah), but it still starts and runs so i'm assuming I haven't stuffed it completely. I'm assuming the current tune has stuffed it (running super rich) Has Wolf 3D V4 but temp sensor is plugged into cold start or something like that so it's pouring the fuel in, been running like that for several months now, was gonna wait till I got turbo setup and save money doing tune in 1 hit...
Questions: Was gonna go turbo very soon but out the window cause of costs of this now, but was going to get ARP studs and cometic head gaskets, which I may as well get now that i have to get new head gaskets anyway right? so then I can turbo later if i want too
With reduced compression, will i lose noticable power just running the car N/A for a few months at least?
Tuesday, February 10, 2009 - 10:14 am, by: Simon Martin(Commander)
Well Scott, being the 1uz pro he is, as he has several high powered turbo 1uzs at the moment and builds them for a living says anything over 7psi and the standard gaskets don't hold up too well. At this stage I won't be running any boost, cause turbo project is on hold due to funds and other things... But if I decide to go forced induction down the track, i don't have to change the head gaskets AGAIN...
Also the motor and box are gonna be out of the car so at least I can check everything over and change the head stuff while the motor is out
Andrew Ferres Goo Roo WA '90 C-F Celsior V8, '84 Soarer V8, '91 Supra V8
Tuesday, February 10, 2009 - 10:46 am, by: Andrew Ferres(Peewee)
Justen (one among a few) has successfully run over 15psi for about 3 years now on a stock motor. Its ALL in the tune (assuming the motor was in good condition beforehand). The old school thought of hi-comp motors not liking boost is now just that, old school thought.
The reason I say can cause more issues is when you jack up the heads with thicker gaskets, the water bridges and the intake manifolds don't as perfectly (small issues) but the big issue is that the cams are now no longer perfectly timed. One side will be slightly advanced, and the other side slightly retarded. It can be corrected with adjustable gears, but thats yet another expense.
Personally I'd just get some Cometic MLS stock thickness gaskets.
Tuesday, February 10, 2009 - 12:34 pm, by: Daniel Clarke(Dieseltrain)
PLenty of guys running 10-15psi on stock motors . Its all in the tune and the fuel used. Compression isnt a bad thing with forced induction, its gotta be tuned right and intake temps kept down .
Thursday, February 12, 2009 - 01:21 pm, by: Damian Ware(Frozenpod)
Question, why is it all factory FI engines run lower than 10:1 comps?
The latest factory FI engines from what I can gather run around 9-9.5:1.
Using an online calculator indicated pending how much boost that around the 9:1 on 98 fuel would be suitable.
I'm not saying it is possible to run higher comps and FI and be reliable but wouldn't it be optimal to run slightly lower comps which would allow more timing in the upper rev range without detonation.
In the even of replacing a head gasket wouldn't it be smart to use the lowered comp alternative?
Andrew, how does this effect cam timing, doesn't the cam in relation to the piston position remain the same with a thicker head gasket?
Andrew Ferres Goo Roo WA '90 C-F Celsior V8, '84 Soarer V8, '91 Supra V8
Thursday, February 12, 2009 - 02:19 pm, by: Andrew Ferres(Peewee)
Everytime you raise the head up, the distance between the cam pulleys and the crank pulley and water pump pulley increases. This puts the cam timing it. It may only be 0.5deg (or even less) but given that one advances, and one retards, the difference between the two is double. This will affect tuning if you are on the limit.
The chamber is designed to work a head gasket of stock thickness. By putting a thicker head gasket in there you are upsetting this design.
The proper way to lower compression is to use low comp pistons. But by the time you do that you are probably running forged pistons anyway and as such it will be fine with the higher compression.
Higher compression means the boost comes on earlier and is better to drive off boost.
The old way of thinking is lo comp, high boost, and some tuning (like a SAFC or similar). The new way of thinking is hi comp (relatively speaking) high boost, and decent tuning (on a decent ecu).
Have a look at all the LS1's with boost. Most of them run stock compression (10.5:1 from memory), and they make plenty of power.
Thursday, February 12, 2009 - 02:29 pm, by: Damian Ware(Frozenpod)
Arh, I didn't think about the belt. Still being a toothed belt I would have thought it would simply be streched more which will be taking up in the tensinor.
That being said there is a slight change in timing with a new and old belt due to the change in strech so I can see it could be possible.
As to cahmber/piston design maybe newer engines are better in this regard. 1uz was released in 89 and perhaps the engine technology wasn't designed with this in mind so lowered comps may suit FI??
Certainly having full timing control is important Simon has a wolf so he should be fine.
But still pulling more timing with higher comps is going to drop the power as well. Lower comp running more timing may produce more power pending the boost level.
Yes some high comp motors are running boost. I have seen a 11:1 built ford motor running boost but it was only 4psi and they wanted to go to 6psi but detonation was preventing it. Not to say with better fuel it wasn't possible but was it optimal??
Andrew Ferres Goo Roo WA '90 C-F Celsior V8, '84 Soarer V8, '91 Supra V8
Thursday, February 12, 2009 - 02:38 pm, by: Andrew Ferres(Peewee)
Your lines of thinking with the belt stretch are right, but with the thicker head gaskets, a stretched belt will only make things worse.
Damian Ware wrote on Thursday, February 12, 2009 - 02:29 pm:
But still pulling more timing with higher comps is going to drop the power as well. Lower comp running more timing may produce more power pending the boost level.
For sure, but unless he's going to more than 15psi he will be better off with stock compression. (IMO)
Friday, February 13, 2009 - 09:55 am, by: Simon Martin(Commander)
I really have no idea. As Damian said I have the Wolf so I'll be able to compensate for out timing.
That said, I asked Scott when I rang him about gaskets and he said Definitely get the metal ones now, otherwise you'll be doing it again down the track...
He runs a Twin Turbo track 1uz in his Cobra, among many other 1uz turbos he's done and he breaks stuff often, he said to go with the metal cometics and i said 'ok' and he's not the kind of guy that will try and make a buck out of you. He's not some backyard mechanic, well, actually he does work out of his backyard per se but he's not dodgey, he does stuff properly.
But anyways Time will tell. Should have motor out tomorrow morning, then we'll see what the damage is hehe
Simon Martin TryHard Queensland 1UZ MX73 Cressida 5spd
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