Generic *budget* low boost turbo build

[mullett]

Let's pretend that I want to put a small, low boost (5-7psi) turbo on a small (1.6L) motor, to give it a bit of midrange shove. It doesn't need to be fast, but it does need to be do-able with the standard ECU. Here's the limitations:

Log style manifold (because it's easy)
air/air cooler
Factory ECU (which CANNOT see more than 4-5psi boost)
Factory injectors (with the possibility of an aux injector)

So here's the problems that I can think of:
Need to prevent the factory MAP sensor seeing more than 4-5psi
Need to provide fuel up to a max of 7 psi
Need to retard ignition? Not sure, but don't want it to ping...

Questions:

Will a rising-rate reg cut it?
what's a good (read: cheap) way to run an axillary injector?

Currently planning on using a MY04 wrx turbo, hopefully that will spool nicely and the factory gate isn't set too high...

Help!

-RM

[oldcorollas]

why do you have to stick with stock ECU?
megasquirt has built in MAP and they are cheap.

other option is interceptor that can advance/retard timing... or if it can only do one of those, then change the base setting so you can reach all the values you need

[mullett]

Stock ECU because fuel economy, reliability, and ease of use/instillation is important.

-RM

[oldcorollas]

i don't see that any of them are issues wire the MS to plug into stock ECU plug...

[mullett]

Haha, the installation time, tuning time and crappy fuel economy are issues...it's my daily! And I do a lot of kays...

Also, all the nice things like cold start, idle control, etc etc that I'd never manage to program correctly...I've got the supra for messing around with properly

-RM

[woggin]

FCD so the ecu doesnt see boost past a certain point and a rising rate fuel pressure regulator to take care of the additional fuel?

[mattysshop]

i have been wanting to do this to my AE92 csi 4afe for ages... i know the map sensor will up the voltage to a full 5v once it gets to about 6-7psi.. injectors and a raising rate reg are easy to come buy..

the only thing stopping me personally is the timing issue.. short of a simply piggy back like a $300 emanage.. i can't get around the timing advance which would most definitly kill the piston's as the boost comes on and timing curve is still going strong..

i'm not sure what 'total' timing it sees, but even if i can retard the base timing to say 1 or 2 deg, my fear is that it will still have too much advance over the curve and detonate the bastard to hell..

[JustCallMeOrlando]

Haha, the installation time, tuning time and crappy fuel economy are issues...it's my daily! And I do a lot of kays...

Also, all the nice things like cold start, idle control, etc etc that I'd never manage to program correctly...I've got the supra for messing around with properly

-RM

Haha, irony being I got better fuel economy with the Adaptronic What car is it, and how old is it? Older cars got away with more because they weren't as precise.

[mullett]

Absolutely, I have great faith in the adaptronic, if I had the time/budget I'd happily replace the factory ECU with one...but I don't in this instance

*grumbles quietly*

*it's a G16B motor in a Vitara*

-RM

[mullett]

FCD so the ecu doesnt see boost past a certain point and a rising rate fuel pressure regulator to take care of the additional fuel?

That's pretty much what i had in mind, but are the standard injectors going to be able to handle such a massive increase? Theoretically 7psi will need 50% more fuel than WOT...

-RM

[Duk]

That's pretty much what i had in mind, but are the standard injectors going to be able to handle such a massive increase? Theoretically 7psi will need 50% more fuel than WOT...

It'll probably need more than that.

Really speeking, if you have't got a decent means of supplying additional fuel evenly to all cylinders and control of ignition, you won't end up with a reliable machine.
Maybe look at getting an AEM Fuel/Ignition controller http://www.aemelectronics.com/engine...oller-f-ic-12/.
Get your hands on some 4AGZE injectors (minimum).

[mullett]

Hmmm, that looks like a good bit of kit. The other option was an SAFC, but I don't know if that could be calibrated to work with a higher capacity MAP sensor?

-RM

[Duk]

The trouble with the likes of the SAFC is that they fudge the load sensor signal to achieve a change. If you fit bigger injectors and then bend the load sensor signal to get decent AFRs then you will be adding some decent ignition advanve too, because the ECU thinks the engine is at a lower load.
That could be dangerous for your donk.

Also, you may be trying to get the standard computer to work at a load sensor voltage that it doesn't have when trying to get it to idle with decent AFRs.
My AFM 4AGZE idles with a surprisingly low AFM voltage (dropping voltage with increased load).

Unless it's had a big upgrade recently, the SAFC doesn't control ignition timing, well not directly and intentionally, anyway.

[oldcorollas]

meh, megasquirt can work with your stock sensors (90% of the time).. wire plug to fit to stock ECU, and then can swap back later.. no wiring changes.

[mullett]

Yup, exactly. Having a look though, I think the ignition timing on this motor is quite basic. There's only two output wires from the dizzy...

-RM