power output

135kwtegem · rice boy Joined: 06 Mar 2002 Posts: 13

I have a te gemimi with an import sohc G200 in it.
It's obviously fuelinjected and i"ve added a turbo.
The problem that I'm having is that I cannot genetrate any more power when I increase the boost. On the dyno the manifold boosted to 33psi but the engine couldn't have because it would have blown and the computer is set to stop it at 20psi. What is my problem? Have Ireached the maximum flow for the standard throttle body and plemium?
Your thoughts would be appreciated.

Badger · tinkerer Joined: 13 Feb 2002 Posts: 155

yeah I would be a bit worried about that. is that 135kw at rear wheels or flywheel? my 1600 (EFI) has 100kw @ flywheel (give or take) so you should be able to get 135 with just the NA 2L IMHO!
regarding the flow, for a given restriction, the flow is related to the pressure, so increasing boost will give more flow ( hence the idea of a turbo!) and therefore more power.
I think that you have a problem, but I have no idea what!
can you give more info on your setup, and what you are doing to get more power?

135kwtegem · rice boy Joined: 06 Mar 2002 Posts: 13

That power output is at the wheels. So the flywheel power would be more like 170kw.
I am aware that having a turbo increases the flow but at some stage you get to a point where no more air can go through a hole of a certain size. It's just like a hose only so much water can be carried thorough a certain size.
My setup as it stands.
low comp pistons
td05 turbo (WRX)
vl turbo injectors
truck intercoller malpassi fuel reg
Piazza turbo manifold
microtech ecu.
as i"m looking at the dyno report now the boost increases in a uniform manner ie. 3.41,6.27,11.01,21.36,30.62,32.86, and finally 33.56 psi.
This is ofcourse the boost in the plenium not the engine she'll only take about 20 pound I'd say.
Hope this helps

Badger · tinkerer Joined: 13 Feb 2002 Posts: 155

>at some stage you get to a point where no more air can go >through a hole of a certain size. It's just like a hose >only so much water can be carried thorough a certain size.
no no no, the amount of water/air depends on the size and the pressure.
think of your garden hose turned on. the water comes out slowly. if you decrease the size of the hole ( ie put your finger over most of the hole) the same amount of water comes out, but it is under much more pressure. Or if you increase the pressure with the same size hole, more water comes out.

as for your problem: the boost increase: is that during a dyno run? (ie boost increased with rpm) how was it measured?
it seems strange, the boost should start low, and then as the turbo spools up rise to the limit and then stay there.
what are you doing to the wastegate to keep it boosting?

135kwtegem · rice boy Joined: 06 Mar 2002 Posts: 13

If what your saying is about hose/inlets is true there should never be any need to increase the size of your manifold. All you need to do is up the boost.
is that Right???
anyhow regaurdless of this the wastegate is somthing I hadn't really thought of. The acctuator is 9psi and it just bleed of with a fairly crued tap type valve.
The increase was on the dyno and they were try to increase the boost. As for how it was measured by the dyno I'M unsure, I wasn't actually there. I't might be a good idea if I check with my mechanic and see what the bleed off valve was actually set at, because the boost dosen't sit steady like you said it just keeps increasing with engine speed untill you back off.
I'll let you know where the dyno measured the boost from. Your probebly right it could be the wastegate.
thanks

Badger · tinkerer Joined: 13 Feb 2002 Posts: 155

you won't need to increase the size of your manifold, except for fixing harmonics, reflected pulses etc. there is a whole bunch of other stuff happening. if you improve the flow through the inlet then you can get more air in with the same boost.
I would be really worried if I left my car at the dyno and when I came back they said they had put 33 psi of boost into it. BANG!!!!
I am seriously worried that the mech has no idea what they are doing.

135kwtegem · rice boy Joined: 06 Mar 2002 Posts: 13

Sounds like you know what your on about.
You may be right about the mechanic as he has already blown it up once.
Are you a mech?

Badger · tinkerer Joined: 13 Feb 2002 Posts: 155

no I am a Physicist, but I do rallying in my spare time. I know a little bit about everything, and a lot about some things...
I seriously think that you should take your car to someone who knows what they are doing as if this guy blows up your engine, it could cost you big bikkies
from what I read this is your situation:

you have the turbo system set up on the gem, working ok.
efi is ok etc, you are trying to get more power out of it.

basics of getting power:
more pressure in the cylinder after bang gives more torque=more power

to achieve this you need to:
increase compression ratio (piston, chamber etc)
get more air/fuel in there

we will deal with the 2nd:
porting, bigger valves, free flowing exhaust, bigger/properly tuned efi/carby/manifolds all get more air/fuel in the cylinder while the valve is open.
cam keeps the valve open longer/opens valves further

and/or increasing the pressure of the air coming in (turbo/superchrger) will put more air in the cylinder and we need to make sure that enough fuel is going in too. the more pressure we have, the more air goes into cylinder.

problems: when pressure in cylinder is higher, then fuel burns better, so at high temperatures, it may spontaneously explode (detonation). power is reduced and damage is assured in time. to fix this we reduce CR, retard timing (so fuel is already burning before explosion), reduce temperature ( intercooler, water injection, extra fuel, cooler spark plugs) or reduce boost.

possible solution to your problem:
1. if I recall correctly the std g200 injectors are quite small, perhaps you are not getting enough fuel in, this is bad, as at combustion pressures/temps, things like valves, pistons etc burn instead of the fuel.
you may need to add another injector which comes on at high boost or change your injectors to bigger ones
2. you computer can't cope with that much boost and doesn't tell the injectors to pump enough fuel, similar situation to above, may be able to solve with bigger injectors to "trick the computer.
3. you are getting detonation which will reduce your power AND destroy your engine! see above for solutions.
4. you are at max boost, wastegate is working correctly, and the method you are using to bypass/trick the wastegate is not working so you are always at or below std max boost(hope this is the one)

hope this helps, but there is not much more I can do. You really need to take the car to someone who knows what they are doing with turbo setups.

Loz · backyard mechanic Joined: 05 Oct 2001 Posts: 943

That is a similar setup to mine. Mines not running yet but I have found out all about the different things involved.
The TD05 is good for slightly over 20psi. Any more and bye bye turbo. The stock injectors are to small for higher HP. The computer will handle high boost etc. Im assuming you have something like an MT8. The stock throttle bodies are big enough to flow enough air for 200+rwkw. It sounds like the duty cycle of the injectors is maxed out and that would explain the max power you have. As for the high boost the reading is taken by the MAP sensor. It is read in psi. You need to take into account the atmospheric pressure of 14.7psi and take this from the plennum boost reading. so it would be about 18-19 psi of boost from the turbo, which is the safe limit of boost from a wrx TD05. Hope this helps.

Loz