Hi all,

Promised in another thread, so here it goes. Finally I have my very own Turbo project, meaning there is one more nut around here In short the plan is to turbo an MPI 1.2 8V engine, fuel it with the P75 ecu reprogrammed to handle wider MAP sensor (2.5 bar, already purchased) and bigger injectors. Fine tuning is going to be made with the help of a wideband lambda and couple of other gadgets. Not sure what to say more, ask questions and I will answer. I decided to start with the exhaust, as this is the only thing I would have real problems managing on my own (do not know how to, and do not have conditions to weld), not to mention I really hate angle grinding, so wanted to be done with it ASAP. Here some pics:

I'm worried about



this. Usual practice is either to seperate the wastegate exhaust off so it takes its own path to the exhaust, or to port the flange itself (so that it joins the main exhaust channel) for better gas flow and thus wastegate operation. Of course, if anything prevents the wastegate from working properly you get a completely uncontrollable rise in boost which will destroy your engine.

I'm not sure -- again -- about re-programming the P75 ECU. There are far better ECUs out there which will take much better care of the engine.

std injectors should be fine aswell id guess for low boost!

Or vent it too air for a screamer pipe lol. Will be nice and loud!

About the wastegate: I already had a discussion about this with some Polish folks on a different forum. I was worried about it too, but then you should have seen the flange that TurboCinqy1250 was using on the same turbo (I actually got one of the turbos, IC, and couple of other things from him).

My point of view is that the wastegate actually opens relatively little during normal operation, and as much as it opens there is enough passage underneath the flange for the fumes to get from WG to the exhaust pipe. Larger openings only happen (to what I could test with a pump and a turbo) with really high pressures on the WG actuator, and I mean high, to my understanding you would have to reach boost level of 1.2 or higher for this to become an issue. My measurements with a pump are of course only approximate and flawed, because they do not consider the pressure of the exhaust fumes that add to the WG opening angle, nor do they consider the actual boost level I want to run, which is still a question. But seeing the flange that Dennis was using it just has to work, provided I get a healthy BOV.

About the P75 ecu: I really don't see what would I miss with this ECU, if it is properly reprogrammed (and this is actually something I am quite sure I can do right). I need to provide the engine with proper fuel under all load conditions and proper static ignition advance. As long as I make the ECU aware of the wider MAP range, there is no problem.

Perhaps the punto 75 ecu does not have sensor inputs required to run a turbo engine properly?

The BOV has no real effect on the wastegate. For the expense of taking a die grinder to the flange, what's the point in risking it?

As for the P75 ECU, it'll probably serve for a low boost car. But I'd want ignition cut (or water injection, or fuel enrichment) on knock, rather than the usual NA ignition retard (potentially suicidal on a high boost turbo), I'd want EGT input, and I'd like some way of the ECU -- or a discreet map on the ECU -- interacting with the wastegate actuator (launch control, wet/dry settings, overboost) for driveability as much as anything else. Most of the aftermarket ECUs -- including Megasquirt -- can do most (if not all) of that.

Well, BOV defo has influence on WG, because it prevents sudden pressure increase in the intake and so sudden extreme WG actuator opening, and in turn WG opening hitting the flange.

Are you saying that in your opinion it would be enough to machine away part of the flange to make more room for the fumes? Because I was thinking this would be a really minor improvement, and if you guys really think this is a concern, then there should be at least a side pipe to the exhaust (I am trying to figure out something nice).

OK, with the ECU, I did not mention that I will also have a module to track EGT and lambda, but only for control, not directly steering the injection or retard. And yes, there will be no option for overboost mode or controlling the WG. But then I was thinking to go rather low/mid boost for reliability.

I found a simple(ish) explanation of the functioning of the BOV in Mark Warner's Street Turbocharging (HP Books).

During normal boost production, the air pressure in the inlet plenum,along with the integral spring, keeps the blow-off valve closed. Full boost pressure is available throughout the inlet tract. During gear shifts, when the throttle is closed, a temporary vacuum is created in the intake plenum. This vacuum downstream of the throttle works with the high pressure upstream of the throttle to lift the valve seat. The excess pressure is then vented out of the BOV.

Click to expand...

So, correctly fitted and functioning, the BOV will only vent when the throttle is suddenly closed: it doesn't sense boost at the wastegate. So, no "psssht" if the throttle is open. Or, if you like, the BOV protects the turbo from power off overboost, the wastegate from power on: if the wAstegate sticks or can't vent enough, the BOV can't save you. Emerald recently ran an Audi TT motor with an undersized wastegate (BOV fitted): it overboosted.

Lots of stuff in the Warner book about seperate(d) and remote wastegates with good pictures.

fingers99 said:

I found a simple(ish) explanation of the functioning of the BOV in Mark Warner's Street Turbocharging (HP Books).



So, correctly fitted and functioning, the BOV will only vent when the throttle is suddenly closed: it doesn't sense boost at the wastegate. So, no "psssht" if the throttle is open. Or, if you like, the BOV protects the turbo from power off overboost, the wastegate from power on: if the wAstegate sticks or can't vent enough, the BOV can't save you. Emerald recently ran an Audi TT motor with an undersized wastegate (BOV fitted): it overboosted.

Lots of stuff in the Warner book about seperate(d) and remote wastegates with good pictures.

Click to expand...

You are right, I am not arguing with this and never was. I was simply thinking reversed logic. If I had no BOV, I would very likely get the WG actuator lock against the flange when shifting gears (and lots of other problems). Having the WG open wide enough when the throttle is open is of course a different story, and it is an issue.

whats the point in restricting the wastegate?

you'll get boost creep! at high rpms the boost will go up and blow the little cinqy engine up

I do not want to restrict the WG!!! It's just that the way I made flange made fingers99 rightfully worried that WG would not function properly. So I am (a) trying to figure out if my flange would be a problem at all, (b) if there is a problem how to solve it without building a new flange and downpipe.

Regardless I of this I was wondering how far does the WG open if there is no sudden pressure increase on the actuator (like closing the throttle without having a BOV).

I should get my hands on this book fingers mentioned anyhow...

to me it looks like your plate will let the WG open more then even the VAD parts as the milled out pit looks deeper. but even without that the WG wont open enough to foul the plate.... ive checked myself

Craig

craigb244 said:

to me it looks like your plate will let the WG open more then even the VAD parts as the milled out pit looks deeper. but even without that the WG wont open enough to foul the plate.... ive checked myself

Craig

Click to expand...

That's what I was suspecting. The previous flange used with the same turbo had a deepening (apparently made with angle grinder, see photo) of no more than 1mm. Mine is 5mm deep. But I am still thinking about making this totally foolproof...

yeh mine was actually milled out but the whole lot it that makes sense but its only about 2mm

craigb244 said:

yeh mine was actually milled out but the whole lot it that makes sense but its only about 2mm

Click to expand...

Do/did you have the same turbo (IHI RHB4 from Astra 1.7)?

Its off an astra diesel but mine is garret. WG side of things looks identical other then the bolt pattern been off iirc

craigb244 said:

Its off an astra diesel but mine is garret. WG side of things looks identical other then the bolt pattern been off iirc

Click to expand...

You wouldn't happen to have a WG side picture, would you?

I've no picture, either, but the VAD ones had a slot milled from where you have the depression to the exhaust -- same width throughout and -- IIRC -- about 3mm deep. It's a long way from being the best approach, but is a common one with integral wastegates. Given that you'll probably find the downpipe difficult to mount in a mill, I'd be inclined to take a die grinder to it.

This set up seemed to serve allanhelen's 1108 high boost tub up to 132bhp or so, but he did have a Greddy boost controller fitted, IIRC.

I think I solved the turbo flange problem in a neat way, I was supposed to have it welded ready on Friday, but it seems flu is floating around the country. Meanwhile I got an oil feed line made (no pictures), and today I test fitted the back part of the exhaust, fits like a glove:







Now it's time to slowly figure out water pipe modifications, so that they do not stand in the way of the turbo, and then air pipes...