DatsunBanana

2 stage boost on R34 - please prove me wrong This is really bugging me since I did a NEO +t conversion and used a GTT ECU. Nearly every discussion says there is 2 stage boost on an R34 - that over XXXX rpm the solenoid bleeds off some air and gives higher boost. That is except a few posts out there saying that the boost solenoid is always bleeding under normal operation and only closes in limp mode and reverts to actuator pressure. There's been some discussion with the +t guys that the pin 104 signal from GTT ECU can do a similar job to pin 104 on the GT ECU which controls the plenum butterfly valve on the NA engine. The R34 service manual clearly explains the way pin 104 works for the GT - it turns the solenoid on at idle and off above 3500 rpm. But all it says for GTT pin 104 is that it's off at idle and at approx 2000 rpm it comes on when the engine is suddenly raced. Where is it documented apart from hearsay that it switches at over XXXX rpm for the GTT? To satisfy my curiosity I went out for a drive with a voltmeter connected across the solenoid plug from pin 104. Under any acceleration ("engine raced") the voltmeter showed a steady voltage (solenoid open). As soon as I relaxed the throttle the voltage dropped to zero (solenoid closed). I took it right through the rev range and as long as it was above 2000 rpm and accelerating the voltage never changed at 4500, 4700, 3500 or any other rpm. If I relaxed the throttle at 5 or 6 K rpm then the voltage dropped back to zero - it didn't maintain the 'solenoid on' voltage even at those high revs. So what I saw seems to agree with the service manual. But where is the idea of two stage boost coming from, I just can't see how it would work on the basis of what the manual says and what I saw in my test. I hope I'm wrong and can have it explained why so I can try using pin 104 to control the butterfly valve.

This pic is a bit dark but you can see the tee in the circle. At the front of the stock NA inlet there's a vertical hose connector with a hose coming up and across to the aac valve. I teed into that hose and took a hose to the turbo water return hard line coming round the back of the block. I took a chance as no-one could confirm what the water flow was like inside the DET inlet but all up and running and my water temperatures are good.

Same as Jap4lyf I have water feed off the coolant drain plug. You can see a close up pic of the fittings earlier in this thread. 1/4" BSPT to BSPP adaptor. 1/4" BSPP banjo bolt which was a good enough fit in the 14mm standard water line banjo and I just bent the line down a tiny bit to reach. For the return I also used a stock GTST return line round the back of the head then instead of the short rubber elbow into the back of the inlet manifold I ran a longer hose to a tee at the barb sticking up at the front of the stock NA inlet manifold. Re-use the coolant if you drain it again. I had to do that with £100 worth of Evans waterless coolant :-)

Just plumbed in a Turbosmart boost gauge and I'm getting ~6 psi just using the stock R33 actuator that came on the turbo. I've disconnected all the hoses related to the inlet plenum butterfly (and disconnected its solenoid switch to be always open) so I can use the feed on the plenum for the boost gauge. I took out a bolt from the accelerator cable support in the bulkhead and fed a thin metal tube through that with hose connected each side. Quite pleased with myself about that cos the perfectly sized metal tube was an off-cut from the hard line that came attached to the R33 J-pipe that I used.

Nice. looking forward to hearing more :-)

When I was running NA I put a GTT cat back exhaust on my 25GT without any issues. No modifications needed. Before that I had a generic back-box and it just droned. It was a stock GTT exhaust anything bigger won't suit the GT.

Thanks. It doesn't look like there a many spare pins on the plug. If I ever bother to pursue this I'll report back. You might persuade me yet to look at a Nistune :-)

Sorry for reviving an old thread but it's one of a few places other people searching this subject might end up. I've done a +t on my R34 using a GTT ECU. The butterfly valve in the NA plenum is open when there's no vacuum - i.e. default position under spring pressure. It closes the chamber when vacuum is applied to its actuator from the solenoid valve. Page EC-44 of the R34 manual suggests that pin 104 on the NA goes to ground at idle which makes sense as that will open the solenoid and provide vacuum to the actuator to close the plenum for torque at low/mid rpm. Same page also suggests that the GTT ECU pin 104 gives the opposite signal while at idle meaning that when used on an NA it would keep the butterfly open at low/mid RPM. The manual shows that on the NA ECU it changes the state of pin 104 at 3500 RPM to close the solenoid valve which would remove vacuum from the actuator and let the butterfly reopen under spring pressure for high RPM torque. Interestingly the manual doesn't mention the 4700 RPM figure but just mentions the GTT ECU will ground pin 104 when the engine is raced suddenly :-) So with pin 104 working properly what I'd get is the opposite of what I'd want ... plenum open at low revs and closed at high revs. However my ECU pin 104 isn't grounding at high RPM anyway for some reason. I wonder if that could be due to the error code for the missing boost pressure sensor. I plan to trick the ECU anyway with some diodes so might find out if that makes a difference. Anyway for now my thinking is that all I need to do to keep the plenum open all the time is disconnect the solenoid plug which is what I've done. Alternatively I could just use the plenum vacuum for something else instead of running it to the vacuum canister / butterfly actuator. Any comments on agreement or different understanding is welcome as this is what I've figured out from reading up online and in the manual and from checking the signals I'm actually getting. I also wondered about this ... if I connect the plenum vacuum line direct to the butterfly actuator it will pull the butterfly closed. What will happen when the car hits boost? Will the actuator get positive pressure and push the butterfly open again? Is that a crude approximation of what the solenoid accomplishes or is it a stupid idea? :-) There's a related thread here with a bit more info about the solenoid ... https://www.sau.com.au/forums/topic/271853-midrange-flat-spot/ Phil.

Thanks guys. I didn't phrase my original question very well sorry. I've got working experience in electronics to tackle this myself but just wondered whether everyone gets the pins off an old loom or buys them new somewhere or what? It's been running the GTT standard ECU for over 1000 Km now with timing retarded, GTT injectors, big FMIC and our cold UK winter temperatures :-). A piggyback might be on the cards later and then I'd probably have that done using the GT ECU I still have to avoid all this hassle with error codes but for now just want to trick the GTT ECU as some guys have done with their NEO engine swaps, PFCs etc.

Faking signals to ECU pins to fix check engine light I've done a turbo conversion and I'm now using a GTT ECU on my GT loom. I don't have the boost sensor or TCS so I get the check engine light. I've read about the way people use diodes/resistors to fake a signal to the correct ECU pins (e.g. secret squirrel trick). But how do you put a wire onto an ECU pin when there's no female connector in the ECU harness - just an empty hole?

Can any of you guys who are still NA answer a question for me? I'm not sure if my butterfly valve in the GT inlet manifold is opening and closing correctly now. It's the vacuum operated lever in between the Y pipe. At 4700 RPM the GT ECU sends a signal to the solenoid that operates the butterfly valve. The standard GTT ECU I have should give this signal for the boost pressure solenoid on the same pin and my GT loom should send that signal to the inlet butterfly solenoid - so all should work normally and the signal should change the state of the solenoid valve and move the butterfly. What I don't know is if the vacuum (sourced from the vacuum canister) opens or closes the butterfly. So I'm wondering if the position of the lever on a stock NA when the car is off is the same or different than the position when the car is running in the low/mid rev range (less than 4700). If anyone can check and let me know that would be great. Mine doesn't seem to change position at 4700 RPM. It does move as I rise above idle and it's behaviour changes depending on whether I block or leave open the pipe that goes to the air filter housing (I've got a pod filter so it's not connected to anything). If vacuum holds it open I'm tempted to give it a permanent vacuum supply instead of switched and see if it makes a difference as mentioned here ...

Oh, and on the point about the feed for the waste gate actuator, I had two options, the take-off I added to the J-pipe or the nipple on the standard IC cold pipe that I got off a turbo car. It's normally at the end nearest the J-pipe which is the end I had to cut. But instead of cutting off the pipe and losing the nipple I turned the pipe around so the nipple is at the IC end down by the expansion tank. That pipe is quite symmetrical thankfully. I used that for the feed to the power steering pump. A third option would be to get the air outlet pipe (the alloy elbow from the turbo) off an R34 instead of an R33. I noticed in some pics they have a nipple too. However that would show pressure before the IC so from what I understand that's a higher pressure than actually reaches the intake - meaning the actuator is opening sooner than it really needs to (someone can correct me if I'm wrong).

Thanks Guys. It's not even got Nistune - just a stock GTT ECU with a touch less timing. Not got a boost gauge yet so just trusting that the stock actuator is fairly low pressure. I've asked a mate if he's got a spare gauge but if not I ought to get one really just to see what it's doing and not spiking. The actuator feed is off the J-pipe. Right on the bend there's that large hose outlet. It can be tapped perfectly to 1/2" BSPT thread and I've done that and just put a hose barb in there. You can just about see it in the pic. Ask as many questions as you like and I'll do my best to answer.

Done :-) Have put about 20 miles on it. Lots of careful rechecking for leaks, tightening bolts etc. There are still a few bits of tidying to do but it seems to be running fine. Not gone anywhere near full throttle for more than a second yet but even with light throttle it's very torquey and a completely different car. No lag, great spool noises and I've got the BOV blanked off at the mo so lots of chatter - I'm giggling like a girl. Thanks to everyone in this thread and others for all the help.

I bought 1200mm of AN4 PTFE braided for the feed connected to the tee at the pressure sender like you. I connected there with 90 deg swivel fitting and fed it behind the head to the turbo. I bought the 90 deg fitting after I knew which way the tee hole was facing after tightening. Then I held it to length and cut the excess before fitting the AN4 banjo. I'd say I cut about 10cm off so just like Jap4lyf said, it ends up about 1100mm.

I got enough fitted to start her up tonight - just for a moment to see what would happen. I didn't have the exhaust on - only the downpipe - and it was about midnight so didn't run it longer than about 5 seconds. Pic shows my mad pipework so I can temporarily run it on idle and check for leaks etc. I've got the AFM connected direct to the throttle body so it can still run NA for the moment. There's nothing coming back from the IC to the inlet at all. Once I've checked it at idle, I'll rev it a bit. The air filter is connected to the turbo inlet and I'll see if the turbo spins up. If so it'll just pump the air through the IC and won't go anywhere - you can see I've just got a yellow spray can cap over the IC cold side outlet. Hopefully it'll all work tomorrow when I can run it without fear of waking up the neighbours! I connected to the ECU with DataScan software and it shows error 46 - throttle position sensor - which I think is the traction control. Hopefully I won't get limp mode. Will keep you posted.

I thought about direct voltage - I might do that later but I've done a couple of hundred Kms now with it still NA and Walbro has seemed fine - even a bit more responsive maybe but that might be placebo effect. Anyway - exciting news is, the car is now in bits and I'm past the point of no return. Fittings are now in block for oil feed, oil return and water feed. All adapter thread sizes fitted fine as guesstimated. Manifold and turbo temporarily attached so I could line everything up. Hard water feed tweaked into shape. Hard water return tweaked into shape. Injectors are in. I was going to just pop the Y part off the inlet to do this but in the end much easier to pop the entire top part. Calculated which silicone joiners I need and ordered those. Cut the J-pipe to fit. Adapted the power steering reservoir bracket to move it out the way of the J-pipe and dump valve. ECU is in. Intercooler was already in. Next it's just making up the braided oil lines, making final cuts to IC hard pipes and fitting joins plus a load of gaskets and bolting together to do.

Fitted my Walbro this evening. I fitted the GSS 341. In hindsight I think the 342 would have been better with the fuel input and output on the same side. It meant the pump was on a bit of angle in the cradle and I used a hose clamp and cable tie plus some fuel hose as a wedge to hold it steady and stop it popping out of position. Hopefully it'll stand up to it. I also had to cut the hard pipe on the cradle because the Walbro was too long to fit. Did any of you guys who fitted a Walbro have to do that? On the plus side, I expected to have to cut and solder the connector but I didn't need to which surprised me. The Nissan connector in the tank fitted straight onto the Walbro but is that what you've found?

Been thinking about this again as when I looked at buying the hose (braided hose) the end fittings aren't really well suited to joining on to a cut off hard line. And non-braided hoses don't seem up to the high temp at the turbo end. So now I'm thinking I'll use: Tee at the pressure sender with an-4 fitting plus 1mm restrictor. Braided hose to an-4 coupler and an-4 12mm banjo at the turbo end. Standard banjo bolt (not restricted). I also found this post which has an interesting point about adding another restrictor if you find there's too much oil getting through ... http://www.skylineowners.com/forum/21-tuning-technical-questions/216246-garrett-bb-turbos-restrictors.html Do you know if 1m of hose is long enough or does it have to be a bit longer? I see yours is 1200.

Hi. I've not fitted mine yet but I've got stock lines that I'm going to adapt. The feed line is just like your pic - a tiny hole (about 1mm) at the block and a bigger (4mm ish) hole at the turbo end. I'm going to cut the standard line and use the banjo with the tiny hole at the turbo end. I'll run back from there with hose to the tee at the oil pressure sender. So my restrictor will be at the opposite end than stock would be but I don't see that it'll make any difference which end the flow is restricted and I believe one end is enough - whichever it is. As long as there's a restriction in the line/eye somewhere, I can't see why you'd need a bolt with a small bore too. I've got all the important bits now so should be starting when the weather warms up here and will report back on how it goes.

A manifold for a turbo car has just one outlet - into the turbocharger. Blank that off and there's nowhere for the gases to go. Gases have to go through the turbocharger and then out of that through the elbow to the downpipe. An NA manifold outlet goes straight to the downpipe. There is (or at least there was) a supplier in NZ (partsco) doing a coby d12 header for NA skylines.

Aleks, how long was the hose for your oil drain. I need to buy a length of that and I'm thinking half a metre should be enough?

OK - that makes sense. For the last few weeks I've been regularly spraying WD40 on all the bolts/nuts I'll have to undo for this project. Hope that'll ease things a bit.

Aleks, just looking at the position of the nuts on the exhaust manifold. At least one seems impossible to get at with a socket. How did you manage?

Heads up for anyone reading this thread and looking for a DET ECU there's a couple on yahoo auctions Japan at the mo ... A manual currently at 2000 Yen and an auto at 6000 http://page17.auctions.yahoo.co.jp/jp/auction/v478256366 http://page4.auctions.yahoo.co.jp/jp/auction/d209093120