AlanG

Question for users of the above mentioned turbo.

I was just wondering if some of you can give me feedback or go out and check on your cars to compare with what i'm experiencing at the moment.

I have a problem with boost pressure in that from 6000-7000rpm, my boost creeps up to beyond what i perceive to be acceptable levels and need to curtail this.

As it is, if i remove ECU boost control and run on actuator pressure only (std TD05 actuator, 0.5bar), my boost stays at 0.5 bar until about 5-5500rpm when it starts to boost creep to approximately 1.4 bar by 6000rpm. This is fine so far cause it's more or less my target boost pressure,but from just over 6000-7000rpm it creeps up further to a whopping 1.9-2.0bar in the last 100-200rpm!!

With the actuator removed, this allows the wastegate to open further than is allowed by the actuator due to its' stroke available from the actuator rod, but i still have a problem with excessive boost at the top end.

With the actuator disconnected i have no boost at all until 4700rpm ish when it starts to build up steadily to a still whopping 1.6 bar at 7000rpm! This is with actuator fully open!!

So...there is obviously back pressure there allowing the compressor to make boost, but i run a 3" exhaust system from the turbo back, so feel this should be big enough.

Now..to confuse issues, the downpipe is a 3" Revolution twin dump effort which has been opened out to become an open neck but is not so open as say, a Hayward and Scott. But with previous tests in the past, the Revolution downpipe produced less back pressure than the H&S. Odd, i know, but true for my car.

The Revolution exhaust has one silencer in the system but i have added a further silencer to reduce noise levels. However, the additional silencer has a 3" bore ID pipe, same as the rest of the system.

So...can we have a discussion on what could be causing this problem and what the cure might be? Will porting the wastegate be enough? Bearing in mind you're very limited to how much you can port the available outlet. Should i look at clipping the exhaust wheel to calm things down?

I also have to add that in the past with std headers (ported), my peak power readings were always at 6100rpm (UK '99 car),but with headers on, it peaked at 6800rpm. This figure was with a relatively steady 1.38 bar of boost which was maintained from approximately 4000rpm. It was also achieved with a Turbo Dynamics turbo, the TMI-141S, which is i believe identical except for use of a Garrett compressor wheel as against the 20G, so exhaust side should react the same way. (I think)

This overboost issue then may not be much of a problem if i still had the std headers on, since the car would be peaking around the 6000 mark (and there's no point in hanging around for the other 1000rpm), but with the headers it is really really strong from 6000-7000rpm.

Alan

john banks

I would port the wastegate first and then try it with the wastegate penny flapping about with the actuator arm disconnected.

If it is then satisfactory then you could reconnect the actuator arm. If it boost creeps again then you could move the pivot as we discussed.

If not satisfactory I would try to port the wastegate even more and use a larger penny.

If still not satisfactory you could consider a clip which on my car completely quelled the top end boost but also killed spool up and gave no power gains, so I would avoid this if at all possible.

AlanG

John

I checked what the boost was doing today with no wastegate actuator connected and the wastgate held open wide to see if it was worthwhile altering the pivot point for the actuator, but as you can see from my findings, at the moment it would be pointless doing this.

I'm unsure if porting the wastegate will improve matters to the extent i need, since there is not much material you can take away on the exhaust housing to allow the std *penny* to seal against.

At the moment there is, at best, between 1-2mm sealing area for the *penny*.
As for a replacement, larger *penny*, where do i get one and how do you change it without having to butcher the original setup and make a dogs dinner of it?

Alan

john banks

Andy ported his and mine eccentrically as there appeared to be more material that could be removed but still retain a seal. We never looked for or found a source for *pennies* as there hasn't been the need so far. A small increase in diameter could go a long way towards reducing boost creep and IIRC made Andy's manageable when it wasn't previously. I think Andy also did some careful mining inside the wastegate channel also.

The suggestion for moving the pivot was after doing the wastegate porting if it was satisfactory with the wastegate flapping open but not when reconnected to the actuator rod.

If all this doesn't work then you could try a clip or an external wastegate? Can't think of other options. This problem could of course be revisited with the bigger engines.

[Edited by john banks - 10/20/2003 4:01:09 PM]

AlanG

Appreciate what you are saying John.

Do you not think though, that the pressure i am seeing is a bit excessive and that the small increase in wastegate diameter may not be enough to allow the volume of gasses required to escape quick enough?

Alan

AndrewC

This place does a 34mm wastegate penny for MHI turbos.

Andrew...

AlanG

Can anyone tell me what is the std diameter of the hole for the TD05 exhaust housings' wastegate?

I didn't appear to have a problem on the boost side with the TMI-141S from Turbo Dynamics, but i wasn't looking or testing the turbo to see if there was an issue.

Mark (Aigin), if you have read this thread. Does the TMI-141S come with a ported wastegate or does it depend on what use the turbo is being put to?

Alan



[Edited by AlanG - 10/20/2003 4:23:27 PM]

AlanG

Interesting site Andrew, thanks.

Now all i need is for someone to explain what all the variations on exhaust side mean (7cm w, 8cm w ??)and what i should be looking for!

*Edited to mention i should have looked at the bottom of the page first to see the *penny* before clicking on "turbo parts" and seeing the different options for exhaust housings!!*

Alan

[Edited by AlanG - 10/20/2003 5:00:19 PM]

john banks

ISWYM Alan. But what else are you gonna try? When I last looked with Andy there appeared to be quite a lot of meat that could be ground off inside the wastegate channel.

Another option could be an 8cm2 turbine housing with Subaru bolt pattern (it is a Trust/Greddy design made under license from IHI who own the rights to the Subaru bolt pattern apparently). Forced Performance in the US were selling 20Gs with this (so larger AR than the 7cm2 we have). But they had trouble getting them and had back orders for turbos never mind supplying me just a housing. Shame, it could be ideal to get a bit more power and reduce creepiness and surge.

[Edited by john banks - 10/20/2003 5:01:20 PM]

AlanG

Thanks John

Is there no other suppliers for the 8cm2 housings?

'Scuse the ignorance, but how would a larger exhaust housing help increase the power? Would this not make the unit a bit laggier?

(And i know how you hate lag!)

Alan

Turbo_Steve

I am in a similar boat with a regular TD05-16G and H&S 2.5" system. Starts to creep at about 5500rpms. The trouble is that the OLD turbo was a TD05 too.

Interestingly, before I put the new one on I did notice some startling variations in the amount of metal on various facets of the exhaust housing.

Having been through all the above diagnostics, and after a chat with Mark @ Lateral he suggested I try a swap of exhaust housing for my old one, which did not have this problem. Although this doesn't help you with your Hybrid, it does show that there appears to be a significant design variance in the exhaust housing manufacture.

If possible, I will try and get some photos of the two exhaust housings next ot each other.

[Edited by Turbo_Steve - 10/20/2003 5:13:14 PM]

AlanG

Are you saying that there may be different 05 exhaust housings available?

I've only seen two variations of housing and that was the different types of locating pin for the actuator, though i never looked at the rest of the housings.

Alan

ustolemyname??stevieturbo

iTrader: (1)

I dont think its the size of the wastegate openeing, more the route the gasses have to take through it.
You can go a little bit bigger with the opening and retain a good seal, but I think that smoothing the exit path is of more benefit than enlarging the hole.
As std, it has to do a complete right angle to get out. Smooth this off and it should give you control back over the boost.

Ive found that if you open the hole out too much, it can make the turbo laggier, possible because it isnt sealing as well as it should when closed. Ive seen this overboost problem with a few TD05's porting alone has always cured it without enlarging the hole much.

AlanG

Thanks Steve. Appreciate the feedback.

I should be concentrating on the path inside the housing then to allow a better path for the gasses to take?

{wonders} What the heck am i going to use to grind away inside a housing??
{wonders}

Alan

David_Wallis

die grinder.

do the big and small wheels have difference housings?

The core and exhaust remain std yes? just front compressor and housing change?

I dont believe going to an external wastegate is a good idea with that housing..

you could change the housing to be a non gated one which would then make it smaller??

Eitherway I dont think that is the issue and if going for an external wg then do it properly

David
David

dowser

If you end up taking the d/p off again, is it not worth replacing it with an open necked version?

Richard

AlanG

Richard

I have tried an H&S open neck 3" downpipe in the past which i expected to improve matters due to the greater open area, but actually made the situation worse, so reverted back to the Revolution pipe.

Alan

[Edited by AlanG - 10/21/2003 2:09:02 AM]

john banks

Just my understanding - feel free to correct anyone if I am mistaken

7cm2 refers to the nozzle discharge area onto the turbine I believe. So 8cm2 is another way (MHI's way) of expressing that the turbine housing has a higher AR, lower gas velocity = more lag, but less back pressure and so potentially more power IF this is the limiting factor. In addition, the larger housing is supposed to also be a cure for boost creep. There is loads of info on TD05/06 turbines and housings on the US DSM turbo sites.

7cm2 is analagous to P18 and 8cm2 is analagous to P20 (but obviously they are not the same (as P18 is considerably bigger than 7cm2 nozzle, the MHI turbos get their exhaust gas flow potential from using larger wheels (of relatively small trim in a relatively small AR housing), the VF series use a smaller wheel with large(ish) trims in large(ish) housings). This is why I was interested in mating a P18 or P20 housing to a TD05 turbine, but the 8cm2 housing should be better if we could get it as it fits perfectly with the TD05 turbine we already have.

I've not been able to find other suppliers/manufacturers of the Subaru bolt pattern 8cm2 housing, but I would love to try one.

[Edited by john banks - 10/21/2003 9:16:11 AM]

MorayMackenzie

How about an 8cm2 housing with an external wastegate... I suspect that would work pretty well.

AlanG

Has anyone tried this? or willing to organise sourcing these parts? as i am willing to try it out, subject to reasonable costings.

Alan

David_Wallis

I belive thats what pat was using.

David

AlanG

If that is the case, could you direct him to this thread to give some feedback?
I'd be interested in any findings on it.
Thanks

Alan

David_Wallis

seem to remember it was a greddy / hks housing iirc..

David

David_Wallis

bump for pat.

AlanG

Thanks David. Appreciated.

Alan

pat

The turbo I was running is a GReddy TD05H-18G with a larger (TD06-esque) compressor cover, but I'm not sure if it's a 7 or 8cm^2 turbine housing. The nearest I could find to this kit was a similar (if not identical) kit by Bozz Speed, and it includes a GReddy external wastegate.

Never suffered from any boost related issues (not sluggish, no creep, no perceptible EGBP issues). I'm not sure what would happen with it if I had run more boost, never really wanted to stress a stock MY97 UK lump, it comfortably exceeded 300 BHP at around about a bar of boost, but I did try it once or twice at up to 1.6 bar... got a lot of blow-by and created a huge amount of white smoke (breather was blowing oil onto the downpipe... oops )

Cheers,

Pat.

dowser

What about this?






<THE BLURB>
Unlike any other open loop external wastegate kit DNP close loop external wastegate kit is quite. It improves a turbo lag, improve a boost control system , no more over boost!!.

High flow uppipe design to fit US WRX: stock location EGT fitting, 2.5" diameter, extra think flange, port match turbine housing inlet .

Twin drop downpipe design from a race application subaru, stock mounting location , easy access O2 sensor location , flex section for easy fitment

This kit includes
- Twin drop downpipe
- External wastegate
- Uppipe
(For off road use only)
<END BLURB>

US$999....and looks like I can get 30%

Richard

AlanG

Thanks for the info Pat.

Reading your post it comes across that it didn't perform as well as you'd hoped it would in your application, but did you move on to something else or try the unit on another engine?

Looking at the pictures Dowser has put up, it would appear trying to fit an external wastegate in the manner of the fabrication shown may prove to be a little on the tight side if it fits all in say, my car (classic shape)

Do you have any pictures Pat which can show just such an installation? Those that i have seen utilise an offset turbo with inlet pipe to the side of the inlet manifold and hence provide a bit more clearance at the bulkhead area, but those shown above have the turbo facing the factory intention.

Alan

MorayMackenzie

I adopted the turbo when Pat started project 33B.

Project 33B's design required more than one turbo, hence the hybrid became surplass to Pat's requirements, so to speak. I was fortunate in getting the chance to adopt it. Thank you again Pat!

[Edited by MorayMackenzie - 10/22/2003 4:59:30 PM]

AlanG

Thanks Moray

Do you use it just now and what year car is it in?

What do you think of it?

Alan