Controlling boost via the ECU and a 3-port solenoid?

[HermaN]

Been speaking to quite a few lads around here who have been complaining that the bleed type boost controllers are too unreliable/poor and that the electronic ones are too pricey for some of them. This got me thinking. On Evos using EcuFlash you can replace the original 2-port solenoid for a 3-port and setup the desired Wastegate Duty Cycles, Boost Desired Engine Load, etc, etc in order to get the stock ECU to control a 3-port solenoid and in turn keep the boost exactly as you want it very accurately just like a stand-alone boost controller, but with only the price of having to buy a solenoid and nothing else.

Could this be done on the Nissan ECU? If it were possible I reckon A LOT of people would use this feature, because it gives excellent boost control, for about £70 for the solenoid, where as a normal crappy bleed valve is £50 and a standalone controller is no less than £200 over here.

Thoughts people?

[Fordy]

i've measured the resistance of both a gizzmo mac solenoid and a stock s14a and the resistance is 1-2 ohms difference

Just need to cut the connectors and fit push on terminals then i'll do some investigation work on the road.

It has been investigated in a thread on here before but with a stock soleniod iirc

I should have chance to do it one night this week but sadly wont be able to log the boost as i dont have the gear to do that yet

[PL]

You should be able to do it with some of them. The only proven one is S15. My mate's car is running with boost control via factory solenoid and it works quite well. It IS a little fiddly to set up - but if you know your stuff it's not hard. You need to adjust the sizes of the factory bleed jets to allow boost adjustment at higher than std boost levels. Som einfo towards the bottom of this page:

http://www.plmsdevelopments.com/customers/gf_s15.shtml

This will only be possible on the engines that use a "proper" boost control solenoid. S15, S14a and R34 use them (many of them (S13) only use the boost control solenoid as an emergency boost cut rather than continuous boost control). Then it's a matter of working out where the boost control maps are. S15 originally had the wrong address but I did a bit of bench testing and (with Matt's help) got it working.

Theoretically S14 shouldn't be too hard to get going. I've not done any bench testing though. Probably more likely to get R34 going first though - cos Matt has an R34. And it could benefit from proper boost control as it currently spikes quite high before settling to 15psi up top. Be better if we could get a nice steady 15 all the way. Or maybe start at 15 and ramp up slightly up top. Although it makes a handy 300rwkw already!

They're not closed loop boost control though. Well, S15 wasn't anyway. Not even load based. It's a simple 2D map (despite what it looks like) of duty cycle vs RPM. It does work though.

Watch out if you do any bench testing though - the factory solenoid has an internal diode across it to stop the inductive spike that happens when a coil is turned off. This protects the driving circuitry - but if you connect it backwards it'll smoke the driver. I can't remember if Mac valve use this diode. I don't think they do...

PL

[Matt]

That would explain my R32 GTR boost solenoid just stop working when I used an injector to simulate the coil. That just stopped responding... which means I've burnt out the solenoid in my bench ECU

[Fordy]

may have to dig out an old scrap ecu to test things with then and hope for the best

Would there be any damage to the nistune board if the driver does blow?

[PL]

I just use an old PC power supply for all my 12V testing. The good thing about them is that they're short circuit protected. So if you hook up a solenoid (with diode) the wrong way it'll just shut down. Then you know which terminal is positive! I mean hooking it directly across the supply - not using ECU.

You won't harm the NIStune board.

Matt, I've got some driver chips if you need to fix your bench ECU. Just let me know the PN off the chip.

PL

[Zuikkis]

You should be able to do it with some of them. The only proven one is S15. My mate's car is running with boost control via factory solenoid and it works quite well. It IS a little fiddly to set up - but if you know your stuff it's not hard. You need to adjust the sizes of the factory bleed jets to allow boost adjustment at higher than std boost levels. Som einfo towards the bottom of this page:

I bolded the "factory bleed jets".. As original writer mentioned, bleed valves usually have problems, whether they have solenoid control or not.. That's why a real 3-port solenoid would be better.

The problem with bleeds is that the wastegate starts opening even when you haven't reached full boost. Bleed leaks part of the air out, so that for example at 1.0bar boost the wastegate actuator only receives 0.5bar.. But if you try a 1bar actuator at bench with compressed air, you'll see that it actually starts to open at 0.5bar or so, and gradually opens more until it's wide open at 1.0bar.

If you have proper 3port solenoid OR some mechanical limiting valve, the actuator receives only 0bar if not at full boost.. Wastegate stays shut until you have reached your target boost. This has dramatic effect on the spool up, with some turbos you can get full boost perhaps 1000rpm earlier. Also the turbo will keep max pressure all the way to the redline, when often with bleed the pressure starts to drop at high rpm..

I usually use these kind of "boost tees",



They are very cheap, easy to adjust (just one knob), and keep the desired boost through rpm range..

[HermaN]

Cheers PL, that's quite interesting and might have to look into that. I have a spare S14 and S14a ECU lying around here. Been meaning to make a bench testing rig for AGES! lol I also have my mates S14a that could be used for some testing, because he is one of the guys that wants proper boost control but without having to fork out for a standalone controller. Will also need to get hold of an old solenoid to test with.

Just ashame that the ECU does not use any form of closed loop feedback for boost control like the Evos. It allows for VERY accurate boost control via the stock ECU, just as good if not better than a lot of stand-alone systems. Also, quite a few stand-alone controllers boost lower on the rollers than on the road from experience, which makes setting them up on a dyno a pain. Where as the ECU boost control is keeps it boosting the same on the rollers and on the road. Can't beat it IMO.

@ zuikkis, that "boost tee" you have a picture of on your post is the exact thing I am trying to avoid in order for better boost control. It's just a bleed valve. Yes they work, but are very in-accurate, don't hold boost well up top the rev range.

[Fordy]

i've got all the connectors i need today at work from 2 audi q7 brake pad's sensor connectors and a diesel dpf sensor for the female side quite a good find in the scrap metal skip

Should hopefully have it all plumbed in tomorrow at work and be able to give it a quick run down the road tomorrow night.... fingers crossed the ecu driver doesn't blow up straight away so i can do some day to day testing

[PL]

Yes, I also use those "ball-n-spring" valves a lot. I find they give excellent boost response. I'll often test on the dyno by first removing the hose to the WG actuator and doing a partial run - making sure I button off as soon as boost comes up. This is then the benchmark for best achievable boost response. Then the valve is fitted and I compare traces. The ball-n-spring valves always match or come very close to the benchmark response.

I just use the "Turbotech" valves that you can get off eBay in Australia but I'm sure every country has their own version.

There's no denying that a properly installed and set up EBC gives best results but unless you know the particular system well, and have fitted it yourself they can become a time consuming nightmare very quickly.

I've found that setting up boost control is one of the most time consuming tasks when dyno tuning. That's one of the main reasons why I like these ball-n-spring valves so much. Cheap, easy to install and use. Great boost response. And unlike so many systems - they just work!

Sometimes I'll fit a ball-n-spring valve just to get the basic tune in place on the dyno (where time is big $$$) - and then fit the EBC later so it can be tuned on the road. Where real world ramp rates often give a more realistic results.

PL