Monday, February 20, 2006 - 09:56 am, by: Hanré Van Rensburg(Silent_knight)
Ok I have a couple of questions I have been wondering about before I start with any big-ish sort of work on the Soarer.
Some of you on here might know the answer to some of the questions which may be of help to me.
1. Would it be wise to raise the compression on the Soarer a tad? Is raising the compression as simple as playing around with different thickness HGs or do I need to look at playing around with pistons aswell?
2. Does any know exactly how much the stock 1J internals can handle? I am not interested to know about another guy who could do this much with his stock bottom end I'm after specifics and ratings.
3. If I decided to do a mild-ish sorta cam grind along with the head being polished and ported will the stock ECU be able to handle it and run it safely or would it be an absolute neccesity to get an aftermarket unit instead?
Tuesday, February 21, 2006 - 11:24 am, by: Chris Davey(Chris_davey)
1. No that would not be adviseable. Increasing compression increases cylinder pressure so you would have to run less boost to have the same cylinder pressure. It would increase off boost performance but if you have stock turbos then there is not much of that.
2. No such thing. Every engine is different and they may have been treated differently during its life. FYI 1jz747 makes 468rwhp through an auto for the last 2 years or so and still going strong. If you want to make over 500rwhp I would advise to use a 2jz-gte instead.
3. head work is usually the last thing you do in a turbo car because you get get a lot better bang for buck with bolt on mods. Also, a regrind of the stock cams costs more than a set of new custom ones. Have a look at Cihan's thread in articles of interest called 1jz working mod path and see how far you want to go
Tuesday, February 21, 2006 - 02:59 pm, by: Mark Paddick(Sparks)
Chris, I don't understand that first reply. Off boost performance is of boost and has no relationship to turbos, stock or otherwise. Better off boost performance has to be a good thing I reckon. And who cares how the cylinder pressure is obtained as long as you get some?
Personally I would go with increased compression. This would allow some decent off boost performance and some pretty spectacular on boost using stock turbos and lower boost. I'm not too sure how this would affect the turbos but at first glance you would be able to get performance and maintain the health of the turbos. This tends to be the approach used by some exotic car manufacturers, a relatively high compression engine boosted at relatively low levels to get performance equal to or better than some highly boosted engines. There is usually enough margin in production engines to be able to increase compression by a reasonable amount with no problems. Replacing pistons will get expensive. If you are going to take the head off anyway then a small surface grind shouldn't hurt. Then you can stick with stock gasket and pistons with a bit more compression. As long as you don't go overboard with big boost the stock ECU should handle mild cams, maybe a piggy back to control fuel. Porting and polishing is not really necessary, just get rid of casting marks and match head to manifolds.
In short I like the idea. Different. Cheap (ish) and should work OK if you don't get carried away. You won't be able to brag about large boost numbers but numbers matter not at all when you car is six lengths in front!
Tuesday, February 21, 2006 - 03:33 pm, by: Chris Davey(Chris_davey)
yeah, probably not worded very well.
Of course it is nice to be different but I just think that unless you can do this surface grind cheaply then I wouldn't bother.
Increased compression will make the car have more power off boost and also on boost. What I was getting at is that, there is very minimal lag with the stock turbos so the off boost performance gain would be minimal IMO.
I think it would be a good idea to increase compression if going to a big single however as it would bring the car on boost a lot quicker.
It depends on what you want out of the car in the end. You need to tell us what the use of the car is and what sort of hp goals you are aiming for. There are many different ways of getting there.
Also, if you increase compression you should have a safer tune incase of a bad batch of fuel.
In short, increasing compression is possible and could be helpful in some cases but it really does depend on what you want the car for and how much $$$ you want to spend
Tuesday, February 21, 2006 - 04:39 pm, by: Benjamin Burgess(Jampac)
If your after low end torque performance, you've really chosen the wrong engine for the job, as 1jz is short stroke big bore engine, its made to rev, not pull stumps out of the ground. Increasing the compression as chris has pointed out is going to increase cylinder pressures a lot more than an increase in boost well. You'd need to get on some engine simulation software to see exactly what cylinder pressures are going to occur with what compression and boost you want as the pressure could be so extreme it'll bust the engine, this is why saab engineers invented this cool engine that has variable compression from 14:1 at low revs sliding down to 8:1 as revs and boost increase. This netted massive gains in power and torque all across the range.
Personally I think you trying to reinvent the wheel, however if thats your thing, go ahead. If you want low end performance then try looking at a turbo or supercharged v8 or even a 1fz-fe donk, but be prepared to fork over big dollars if you get someone to do the work.
I'm of the opinion that porting and polishing is not that cost effective in regards to gains vs cost. It makes sense in a race car, but on a street car, nope makes no sense at all unless you want bragging rights.
As for how much the stock 1jz handles, how long is a piece of string? Its an open ended question as not all engines are created equal and who knows what sort of life yours or someone elses engine has had. Chris's example of 1jz-747 is probably the best you'll get on the possible longevity of the motor, other than going to work in toyotas engine r&d section. You could also pull the entire engine down and run non destructive tests like penetrants, xray, ultrasound, eddy circuits.... but whos got the money for that.
Thursday, February 23, 2006 - 08:47 am, by: Hanré Van Rensburg(Silent_knight)
Hrmmm that's all very interesting thanks guys.
The reason why I ask is because I can probably get a little headwork done for rather cheap through a friend of mine but I was not sure on whether it would be a feasable idea or not.
I haven't found out exactly what sort of prices I am going to be expecting and depending on that I will make my decision.
As for the compressions I was thinking about raising it just a little bit while the head is off by using a thinner HG. Was thinking of going just a little to say 9:0:1 or something similar. No drastic changes.
What I just need to know for now is will the stock ECU be capable of accomodating things like like a little higher compression and a bit of porting or will it not?
I have an SAFCII that I can use but I don't know whether it will be able to do the job properly. Maybe a piggy back unit like the E-manage will but I have no experience with that so I don't know.
Thursday, February 23, 2006 - 10:32 am, by: Chris Davey(Chris_davey)
This could be wrong but I would think that the stock ecu wouldn’t be a good idea with a higher compression motor that also has head work.
Re head work: the MAP sensor is connected to the inlet manifold so it measures the manifold pressure and then determines what fuel and ignition to run with that amount of pressure. If the pressure is the same but the head flows more then there will be more air entering the combustion chamber. Because of this, I would have thought that the engine would run leaner at the same pressure level as pre head work.
Re compression increase: You have to be very careful tuning a higher compression turbo motor. As was said the cylinder pressures are much higher and therefore you have to keep a good eye on air fuel ratio (also use higher octane fuel would help) and ignition timing to prevent knock. In this case, I actually think that the power fc with its inbuilt knock sensor would be a good choice. (Otherwise, do what I am doing and make your own knock sensor) Either way, I don’t think it would be a safe thing to do on a stock ecu. With an emanage and a safe tune then it should be ok though.
Thursday, February 23, 2006 - 11:12 am, by: Benjamin Burgess(Jampac)
Power fc may read the knock sensor data, but it doesn't actually use it to retard the timing if a problem occurs. All it does is flash your engine check light and give you a knock rating on the hand controller. Only a stock ecu with a piggy back would knock back the timing.
Just running the stock ecu only would be pretty silly but as your air/fuel ratios would be all different, and is something the ecu has no idea about when out of closed loop mode, so you would need some kind of tunable management.
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