[Kymb0]

Hi all, anyone have a recommendation on Brisbane's Northside for someone who is good with aftermarket Turbo's? My new toy has a Turbo from a Peugeot fitted but some serious lag on acceleration. When you depress the noise pedal beyond halfway she just dies out. Current considerations are incorrect plumbing, MAP issues, Insufficient fuel from sender pump, higher capacity injectors required. Would prefer to pay someone to look at it than do everything and not succeed.

[Brenno]

What ecu does it run?

[Kymb0]

It's a factory efi engine so it has the factory ecu

[Brenno]

I'd say there's your problem. That MAP can't read positive pressure. I got by with my supercharged g13bb running 5psi by using a rising rate pressure reg but it wasn't great. You also can't change timing manually either.

[Brenno]

I'd say there's your problem. That MAP can't read positive pressure. I got by with my supercharged g13bb running 5psi by using a rising rate pressure reg but it wasn't great. You also can't change timing manually either.

[Kymb0]

It already has a regulator but it's not keeping up. Driving her today she seemed to be a lot more happy. Just avoid the flat spots and hills.

[Gwagensteve]

I think you should consider getting it to a dyno so the car can be run under controlled circumstances and AFR can be checked. The timing is never going to right for a boosted application and as the G motor isn't knock sensed, the engine can't pull timing out if it's detonating.

How much boost is it making?

Trying run an N/A ecu in a turbo application is never going to result in a safe or reliable combination. The best you could hope for is to retard the timing, run a W/B O2 sensor, boost gauge and fuel pressure gauge in car and try to drive around the ECU but I'd rather be driving the car than watching gauges wondering if today was going to be the day.

If it's a G13BB these are hardly easy to find so it's not like the old days where engines were available and cheap.

[Kymb0]

Heh Steve, been a long time. It sits on 4lb on the highway. Yes a Dyno and possibly an aftermarket ECU or if it's too difficult I have the original headers and will take it back to factory. Hence why I need a Turbo Guy

[Gwagensteve]

You really need a good EFI tuner. Any EFI tuner with a dyno will have seen what you're dealing with many, many times.

The symptom of a regulator "not keeping up" would be high fuel pressure that can't be turned down. My guess is that's not your problem. (i.e the FPR is causing a restriction - I actually think this is a real issue wth people running a Bosch 044 pump with stock G motor EFI conversions)

If fuel pressure is falling with rising RPM then the fuel pump/lines are inadequate. How are you measuring fuel pressure under load? it's not easy to do without the car being on a dyno or with an in-car fuel pressure gauge.

*boost referenced FPR's are typically for carb applications where fuel pressure is very low (say 5psi) and if you make more than 5 psi of boost, the fuel will stop flowing. With boost reference, the fuel pressure will match boost and then you can tune the carb "normally"

If fuel pressure is falling with rising RPM, and fuel pressure isn't rising with boost, and you have stock timing, the "flat spots" you are feeling are the engine leaning out. This is a very unsafe condition - the result is high heat/detonation etc. You really need the opposite if you're going to try and get by with stock timing - it needs to run rich to cool the cylinders.

My guess would be the flat spot is around boost threshold. Below the boost threshold will be fine because it's basically just working like a restricted stock motor, so, if anything, it will be a bit rich. As soon as boost comes in though, the engine needs lots more fuel and less timing.

To be honest, I'd remove the turbo for now. The risk you'll break the motor in normal driving or on the dyne is too high. I'd gather some opinions from EFI tuning specialists about what you have and what the cost will be. Nobody I can think of would want to attempt to tune the car in its current state because there is nothing they can "tune" - timing is locked, and they can't adjust the fuel table. All they could do is run it and tell you it's leaning out, which you already know.

I recall reading that G13BB injectors don't have a lot of headroom in them, but that's not relevant now - you have no way of controlling injector duty cycle so it wouldn't matter if it had 150cc or 1500cc injectors in it, if it's lean too bad. If you get control of the fuel table then you can work out how much boost you can use before you run out of injector and decide what to do from there.

If you really want to press on with what you have now, get a WB 02 sensor on the car, ensure you have lots of fuel pump and pay a lot of attention to fuel pressure under load. You need the AFR to be really FAT on that transition to boost. (ever noticed turbo cars will puff black smoke if the owner really boots it? That's AFR's going really rich to protect the motor momentarily on a boost transient) Maybe also lock the timing via the diagnostic plug and take a couple of degrees of static timing out of it.

You have two parameters - base pressure and boost referenced pressure. Increasing base pressure will make the car richer everywhere on the fuel map, even it idle or off boost, and boost referenced pressure will add, say, 1 psi of fuel pressure per 1psi of boost. it's a very crude tuning tool more suited for adjusting for small boost increases on factory turbo cars or, as above, blow through carry applications rather than turning an N/A motor into a boosted motor where the fuel demands are much greater than 1:1. - that is, if you have 40psi of rail pressure at idle, 4psi increase in fuel pressure at 4 psi of boost is never going to carry enough fuel to do the job. In fact, you're working against 4psi of positive pressure in the manifold instead of vacuum at full power (near -15psi) so in reality you're flowing less fuel than stock even with a boost referenced FPR - so you're left with base pressure and removing base timing. Both of these things will make the engine doggy off boost.

That's all I can think of to hold the engine together and I don't think a "wizard" would have any other ideas. With a piggyback ECU you might be able avoid the cost of a full custom loom/ECU but it's still going to a substantial cost.

PS - Brenno had more luck because superchargers are basically linear and turbos aren't - they have huge fuel demand transitions as they spool. They're much more dynamic in their operation.

[rexhunta]

We ran a rising rate fpr on a series 1 g16b on factory ecu with the silly vane afm.

at 4 psi we still found the af/rs to be pretty close, we had a pretty lazy turbo, but still saw around 12.9-13.0 af/rs. Before the last comp we ran 98 with octane booster on top, didn't have any trouble although we managed to have a pretty cold day.

Haltechs are getting cheap, probably best way to go.

I'm all for turbo'ing NA engines, just got to remember to dial back a slight bit of timing.

[Kymb0]

She will sit on 110 kph quite easily but getting there and hills suck the life out of her. I'm concerned that the return to stock might not provide the highway speed I need although it did come with some extractors. We did test the fuel pressure under load and it was apparent that it didn't change at all. It has some sort of flow regulator fitted which I'm not familiar with. I expect it will require an aftermarket ECU and that really is the big question. I appreciate you wisdom and experience Steve.

[Gwagensteve]

rexhunta wrote:

We ran a rising rate fpr on a series 1 g16b on factory ecu with the silly vane afm.

at 4 psi we still found the af/rs to be pretty close, we had a pretty lazy turbo, but still saw around 12.9-13.0 af/rs. Before the last comp we ran 98 with octane booster on top, didn't have any trouble although we managed to have a pretty cold day.

There will be a big difference between MAF and MAP cars in this regard.

With a MAF, it's just measuring the mass of the air entering the engine. depending on the calibration of the MAF (as in how much headroom it has) it might still fuel a car reasonably well under light boost as it's still able to measure and fuel for the amount of air entering the engine. Also, the base timing is readily user adjustable just by twisting the distributor. The input is throttle position and air mass (so that's flow and density) = fuel and timing. It'll still have some resolution above full throttle/full load.

with a MAP, (so a coil pack G13BB/G16B) it's much messier. The computer looks at throttle position, then manifold pressure and air temperature to determine the density of the air and how to fuel and time the car. In an N/A application, the manifold only ever sees vacuum and the MAP is only calibrated to read vacuum, not pressure. I don't have "normal" vacuum figures available for a G13BB at WOT but there will be a slight vacuum in the manifold. basically, theoretically if you could hold the car at full throttle and then adjust fuel pressure and watch the AFM you might be able to get the AFR rightish at full throttle at full boost. The problem is when you're at light boost/light throttle - the MAP still sees no vacuum so it thinks the car is at full throttle, (which you've set fuel pressure for) so now the car is super rich. shut the throttle and the manifold sees vacuum and fuelling goes back to normal control but now it has heaps of fuel pressure so it's super rich and will bog - that's even assuming the injectors have the headroom (which they likely won't) I imagine it should throw a CE light for a MAP fault. The end results won't be very drivable except at full throttle. (interestingly this sounds like early EFI turbo competition cars in the 1980's- the fuel tables were so coarse they were generally mapped at idle, 25, 50, 75 and 100% throttle, which made them terrifying to drive- imagine adding a tiny brush of throttle in a corner and tipping from 75% to 100% throttle, with the accompanying boost)

As has been pointed out, the MAP can't see boost and so the ECU can't see it either.

[rexhunta]

100% my fault there, did not notice the MAP, was reading on a phone. Carry on.

[Gwagensteve]

Yeah no sweat, It had never actually occurred to me that a MAF car could cope with low boost so long as there was headroom in the AFM signal.

[Kymb0]

Ended up going back to extractors on my car. The single point fuel injection just couldn't produce the fuel she needed to run properly. If anyone is after a turbo with manifold that fits a G13 let me know.