Tuesday, December 05, 2006 - 05:27 pm, by: Mark Paddick(Sparks)
That's what I thought. The low compression/high boost will maybe have some advantages but not enough to really make a huge difference and the other setup has other advantages, the main one of interest to me is that it won't cost an arm and a leg to find out.
Tuesday, December 05, 2006 - 06:22 pm, by: Rehan Bandara(Parsec)
the pressure at bottom dead centre is important because it changes the amount of work that the cylinders need to do in compression to attain a certain pressure at top dead centre.
the advantage of the low compression/high boost system is it will make more power at the top end and be more efficient, at the cost of turbo lag.
turbochargers are more efficient than pistons at compression, which is what it comes down to.
I didn't think of the work done on the piston in a turbo setup during the intake stroke. That's an interesting point. I doubt it's a lot, but it's something, and it all adds up.
Tuesday, December 05, 2006 - 07:19 pm, by: Mark Paddick(Sparks)
If it's a standard engine and not new so I don't want to push the top end too far anyway.
If you look at the pressure difference between top and bottom in isolation it does pretty-well cover everything. At least as a close enough approximation. Just about everything that's been said so far fits that with a few provisos which is just about what I wanted to hear. I'll give it a go and see what happens. At the most I lose an old engine that's not needed and a turbo. A smallish turbo properly wate-gated and boost controlled should wake up an old 1UZ in good nick still. It could be pretty quick off the line with a decent auto. In a Soarer it should come close to at least standard TT power. At least close enough to make life interesting. I can't see a downside if the turbo responds to being told what to do properly.
Tuesday, December 05, 2006 - 08:17 pm, by: Rehan Bandara(Parsec)
Any idea what kind of pressures the stock internals are happy to handle?
I guess you can at least run it at what all the supercharged boys do (~6psi)
I have been toying with the idea of selling my TT and turboing a v8 (or a honda s2000) as i'm in a bit of cash at the moment.
are you doing a TT setup? I wonder whether its worth going for headstuds, roller rockers, forged pistons, rods, etc. Everyone i've spoken to tells me the v8s have great stock internals as is.
Ben Socratous Goo Roo SA I am the fibreglass/kevlar/carbonfibre king!
Wednesday, December 06, 2006 - 12:01 pm, by: Lew Radbourn(Marlew)
Rehan; Mate do some looking at every aspect of the 1uz motor then tell me HOW on earth are a set of roller rockers going to fit in it. cause i have no idea how to fit them in there and if i would really want to even try.
Wednesday, December 06, 2006 - 03:39 pm, by: Mark Paddick(Sparks)
Mate, that is the whole point of my approach. As soon as you open up one of these things, or a TT motor, you are up for big bikkies to put it back together. Just a head gasket kit costs more than a new head for some motors! Jut look at an old VW. You can get two new pretty schmick heads for less than the price of a 1UZ gasket set, NEW HEADS, ported even and maybe even somne big valves if you hunt around. And still have enough left for a couple of cartons to celebrate after you bolt 'em on!. (VWs don't use head gaskets so they're free)
You don't want to split one of these engines if you don't have to. You can buy a complete late model with higher compression maybe, for less. With an A/C comp and alternator and steering pump etc, etc. Any one of which, if it fails on your car, will cost more than the engine landed on your doorstep from Japan, to fix. that's how I ended up with this one spare. The old engine wasn't exactly stuffed just needs an A/C compessor ...or not, in a track car. If your really serious just order one of the Lextreme engines. Why would you want to about builing something serious for months on end to save alittle money? Maybe not quite that extreme but unless it's really special one of the Lextreme motors at around $7k for the lower optioned ones is gunn be hard to beat for value. especially the bit about "choose your compression" if you're that way inclined. So I'm not splitting it. So I have an engine with 9.5:1 compression that is OK and all the bits work and it's not noisy so it's not completely worn out and the cooling system has been looked after (the main reason you don't want to buy an OLD engine apart from all the old bits hanging off it. A much newer engine will have done a lot less work and it and all the bits that hang off it will probably be OK. Certainly better than the 15y.o. bits you have now. And the kicker, the cooling system hasn't had time,yet, to corrode away). It is 15 years old so I must remember that!
9.5:1 compression isn't that high and that was when it was new. I can tell you it isn't there anymore and no 15y.o. motor is. but it runs good, compression is even. it's got maybe 150k or so on it. Must remember to stick some 'plugs in it. I has NEVER had new ones, they're still original. There are late model VVTi and equvalent cars (not necessarily Toyotas) runnining that kind of compression out of the factory with smallish turbo(s) running lowish boost...........hang on!!! Wasn't that what I was talking about in the first place!!!??? Without the VVti of course. But it still should work OK albeit a little slower and less efficient and a hell of a lot cheaper, than a current model. It is a 15y.o. car so you would expect that it would be a little slower and less efficient after all. But with a bit of thought and carefull planning we might just be able to do it very cheaply and there's no reason why a design carefully worked out by a private individual, with help where needed, could not in fact blow the doors of a mass produced heavily compromised design. Even if they do have access to better technology and resources they don't use them to best effect 'cos the beancounters get in the way. And there's every reason why the private design could be better....or not. This is why I asked the question in the first place. I needed to know the answer and I will need some empirical evidence (numbers, prefferably honest ones) later to base a few decisions upon.
So far there is a 4 litre V8 with about 9:1 compression at most. Next is a small ball bearing sweet little turbo from somewhere and a bit of welding and stuff. I reckon a side mount factory intercooler (the factory did work out the airflow, maybe a Supra one if available. It'll fit. I'll make it. Should get an old one off the Supra forums cheap. They don't want them and rightly so. Doesn't mean they're useless) and a nice little water spray setup I know of that will be cheap, efficient in water use and effective.
I sort of run out of steam about here but it's lookin' good I reckon.