Tom's twin turbo thread

[longassname]

If you do not have knock but your timing is being retarded then yes it would presumably be caused by a false knock sensor reading and unplugging the knock sensors would make it go away instantly at the expense of leaving you vulnerable to real knock and detonation. You could also pay the $70-$130 to have the dealer hook up the select monitor and take it for a spin and see.

Personally I have worries that it's something more like exhaust back pressure causing fouling of the intake charge due to the overlap of the intake and exhaust valves being open. Since your engine is factory I wouldn't expect it to register false knock unless a sensor was bad.

Originally Posted by SVXtasy

Dp you think this could be my problem? because i am 99% sure i am not knocking because when i put 101 oct the problem did not change at all. i might just try to unplug the knock sensors.

[TomsSVX]

thnx for info Mike

On the note of the overlapping valve timing I wonder at what psi would the stock springs be able to keep the valves shut. Lets say at 6500 rpm with 6-8lbs of boost, are the stock spring rates high enough to keep the valves shut when they need to be??

Tom

[Phast SVX]

Originally Posted by TomsSVX

thnx for info Mike

On the note of the overlapping valve timing I wonder at what psi would the stock springs be able to keep the valves shut. Lets say at 6500 rpm with 6-8lbs of boost, are the stock spring rates high enough to keep the valves shut when they need to be??

Tom

remember that mike has a supercharged SVX....he saw no problems of the such in his blown svx, so it almost has to be a backpressure issue if its a fouled charged you are running into.

sam,
how does the wastegate actuate when you are in a boosted condition. Do you get spike, compressor surge, any of the such? What happens to boost when the engine is around 5,500 to 6?where did you pull the signal for the wastegate from? a direct tap from the pressure side of the housing?


phil

[TomsSVX]

dang... I didn't even think to reference the S/C test package...

Tom

[SVXtasy]

I have been thinking about taking it to place that has a Subaru select monitor. And taking the car for a spin. If it is exhaust back pressure it could be fixed with adjustable cam gear and we could take out some of that overlap right? but if it was back pressure I would be getting very high EGT's and I am not at all in fact my EGT's are a quite a bit lower then what a WRX likes to run at in boost. So this weekend I am going to try to disconnect the Knock sensors and use the eManage to do boost based timing retard. If that does not work then I have a huge problem and I need to figure out how to fix the back pressure. I have a huge exhaust side on my turbo I have huge pipes a huge cat so I don’t know how that could be but you never know.

Originally Posted by longassname

If you do not have knock but your timing is being retarded then yes it would presumably be caused by a false knock sensor reading and unplugging the knock sensors would make it go away instantly at the expense of leaving you vulnerable to real knock and detonation. You could also pay the $70-$130 to have the dealer hook up the select monitor and take it for a spin and see.

Personally I have worries that it's something more like exhaust back pressure causing fouling of the intake charge due to the overlap of the intake and exhaust valves being open. Since your engine is factory I wouldn't expect it to register false knock unless a sensor was bad.

[SVXtasy]

My WG is referenced to the outlet of the turbo. No spike no compressor surge it is a bit lagy because of the huge exhaust side of the turbo but that is expected. The boost stays the same all the way across the rpm range. The car just slows its acceleration so much that by 6000 the is just not moving any more.

Originally Posted by Phast SVX

remember that mike has a supercharged SVX....he saw no problems of the such in his blown svx, so it almost has to be a backpressure issue if its a fouled charged you are running into.

sam,
how does the wastegate actuate when you are in a boosted condition. Do you get spike, compressor surge, any of the such? What happens to boost when the engine is around 5,500 to 6?where did you pull the signal for the wastegate from? a direct tap from the pressure side of the housing?


phil

[Phast SVX]

Originally Posted by SVXtasy

My WG is referenced to the outlet of the turbo. No spike no compressor surge it is a bit lagy because of the huge exhaust side of the turbo but that is expected. The boost stays the same all the way across the rpm range. The car just slows its acceleration so much that by 6000 the is just not moving any more.

You should not be recieving any lag with a .63 exhuast housing. This size housing is often used on 2.2L preludes, the whole design of the t3 exhuast on the t4 impeller is to accomodate smaller engines. If anything you shold be getting rediculously fast spool up. Id start from there in diagnosing your problem

[SVXtasy]

well it is a stage 5 exhaust housing so yes i should be getting lag. 500hp hondas with the same exhaust side dotn spool till over 5 grand.

[svxistentialist]

Originally Posted by wawazat??

Graham has done some great stuff with his car hasn't he Joe? 5 speed, big brake kit with multiple piece rotors, M112 supercharger with beautiful fabrication. Very nice package

Todd

Hey Todd,

Yeah, you are right there Todd. The installation and fabrication are all carried out to a serious degree of excellence. Graham has done a wonderful job with the engineering of the install, and the stumbling block[a big one!!] is this fuelling problem.

Michael has come back with a generous offer of advice and help, and an offer to upgrade the chip to the top spec one. Great news! I rang Graham tonight, and he is getting in touch with Michael.

I forgot about the multiple piece rotors, you are correct there. He has lightweight bells on the bigger rotors.

It is quite possible that the M112 would best be restricted to 7 or 8 lbs as people suggest. I think it delivers about 1.9 litres per rev compared to 1.6 litres for the Whipple. So for the same pressure it will be giving about 12% more air than the Whipple, and so more hp and torque.
{The big pulley he has it running with at present delivers about 3-4 psi}

I can't wait till this thing gets tuned, and Graham gets it on a 4 wheel dyno.

Yo!!!

[wawazat??]

Originally Posted by TomsSVX

thnx for info Mike

On the note of the overlapping valve timing I wonder at what psi would the stock springs be able to keep the valves shut. Lets say at 6500 rpm with 6-8lbs of boost, are the stock spring rates high enough to keep the valves shut when they need to be??

Tom

Two things to consider here Tom. Valve springs are one. The other is the fact that the EG33 uses hydraulic lifters which above a certain RPM tend to bleed down.

Todd

[f1svx]

Hi fella's
Now then if I might speak for myself and Martin(colleague).
I would like to thank Joe for pitching in on my absence, much appreciated but here are the facts.
i have been developing this car for around 4 years, the engine was rebuilt with the pistons skimmed giving a CR of 8.2 :1 then ceramic coating applied to pistons, heads and valves as an insurance policy. This was done 4 years ago and was run for 2yrs 6 months as a NA car, just with a lower CR than standard. Also, obviously (Being British) I changed it to manual.( In which time I have run her as a family run about, and business vehicle for some 30,000 miles).
When, 18 months ago I completed the prototype SC fabrication complete with 440cc injectors. At that point it was giving 9 psi but ran horribly as I knew it would, however there was no one in the uk interested in developing software as a one off at a sensible cost which left me stymed. I have teamed up with Martin to complete the project and take it out of it's prototype stage to it's now finished form. We would like to say at this point that we have no intention of duplicating this installation, so there can be no competition between the two systems in terms of business. And so no conflict of interest
Obviously we watched Michael's project develop across the pond, and we take our hat's off to him as it's one thing to do a job, but being under a microscope and having to explain to every one else exactly why you are doing it this way would take the patience of Jobe.
We want to thank Michael for the help he has given so far. i apologise Michael for not getting back to you, however, i have had a job change a new baby due in a couple of weeks and last but not least a larger pulley to make.
As Joe has so rightly said we are now running the car with only 3.5psi on the standard chip with the Z32 maf and the car runs great @ 8.2:1 CR. Michael, neither myself or Martin understood that the the offered software was the 2 v 4 and took your advice and decided to make the larger pulley first so as to determine the next step. We would greatly appreciate it if you could send the offered upgrade so we can move forward and develop some real horsepower which we know this engine is capable.
Cheers guys
Graham F1SVX :http://www.subaru-svx.net/forum/images/icons/icon14.gif

[Phast SVX]

Originally Posted by SVXtasy

well it is a stage 5 exhaust housing so yes i should be getting lag. 500hp hondas with the same exhaust side dotn spool till over 5 grand.

what is the trim of the housing? your websites states its a .63, i dont see how it could be any differnt size?
phil

[TomsSVX]

I no longer object to this hijacking. it is all relevant to my queeries and now I don't need to search everywhere, I can just look in my thread!!

Tom

[oab_au]

Originally Posted by SVXtasy

I have been thinking about taking it to place that has a Subaru select monitor. And taking the car for a spin. If it is exhaust back pressure it could be fixed with adjustable cam gear and we could take out some of that overlap right? but if it was back pressure I would be getting very high EGT's and I am not at all in fact my EGT's are a quite a bit lower then what a WRX likes to run at in boost. So this weekend I am going to try to disconnect the Knock sensors and use the eManage to do boost based timing retard. If that does not work then I have a huge problem and I need to figure out how to fix the back pressure. I have a huge exhaust side on my turbo I have huge pipes a huge cat so I don’t know how that could be but you never know.

With a turbo the exhaust up pipe is the one to cause the backpressure to foul the inlet. The down pipe, if it is too small will only restrict the amount of boost that can be produced. In this pipe the energy has been removed, and we are only dealing with gas flow. The up pipe is a different story, it is dealing with a high pressure pulse, that will increase as the boost increasess. If this pulse is not considered, the pressure will be present at the oppersit exhaust valve that is open.

For instance, when the #6 exhaust valve opens to release, say a 65 psi pulse into the up-pipe, the oppersit #1 is at the fully open position, looking for a low pressure on the up stroke, and a negitive pressure, about 90 degress later. Instead along comes this high pressure pulse of exhaust gas to flow into the open exhaust valve to pressurise the cylinder , and as the #1 inlet is about to open, the pressure flows through it to the inlet manifold, and the power evaporates. Remembering that this released exhaust pressure, will increase to 130psi, at one atmosphere boost. The EGT won't go up as the as the fouled inlet charge is dropping power.

The design of the up-pipe has to be built so that the two engine pipes join as close to the inlet of the turbine housing as possibable, even to the point of the pipes being D shaped side by side, right at the entrance. And the length of the two pipes are long enought to prevent the pressure from reaching the other side.

Harvey.

[TomsSVX]

WOW good info harvey and we thought you were only good for transmissions

Tom