JasonO

The stock engine does have enough grunt to pull top rpm in factory trim. Looks to me like htere are different gear ratios going around between these cars, which ties in with a converstion I was having this weekend. 4th tops out at 120mph / 7000rpm for me, others I know of get at least another 10mph on top of that.

You're going to try and improve this.......That's a big order Good luck Christian, I look forward to the results.

Correct, which is why I said......

Use the rope trick I mentioned above, exxcept wind the rope the other way around the crank pulley.

discopotato, It's common to run twin 3037's on the Rb26 for 800hp applications, so I think a single would be a bit breathless. Steve, Finished the engine build, and it's incredibly strong, pulls from way low down and is much more driveable than it ever was. It's got a really relaxing delivery, with a stupidly wide power band. But then I took it back off the road, to fit larger injectors, a proper fuel system, and practically all of the Earls hose and fittings catalogue. It's got the 'show' and all it needs now is a proper tuning session to complete the 'go'. I'll post details when it's all together, shouldn't be much longer now.

Steve, You say you did 10k km's on that turbo, what you running now ?

Oh, Just to ad some confusion....... When I say add duty cycle, it may be that your particular setup needs to remove duty cycle. You'll get the idea though, and you can work it out by inputing a maximum (90% ?) duty cycle, then a minimum (20% ?)duty cycle and doing the power run thing. One of them will over boost like mad, the other won't reach the target boost. Sorry, but it is after 6am and I'm kinda tired

LOL

Set them up as you like, my personal preferance is to set 1&2, to my preferred low boost setting, and 3&4 high. Then I set 1&3 with very conservative duty cycles and 2&4 with aggresive duty cycles. This gives me plenty of choices....... 1 = Progressive (smooth) low boost, for poor weather, normal running. 2 = Agressive (On/Off) low boost, for good weather, normal running. 3 = Progressive high boost, for poor weather, spirited running. 4 = Agressive high boost, for good weather, spirited running. The best way to determine the correct duty cycle is through experimentation. Set the desired boost level, and a mid range duty cycle, then do a power run. Check to see if you made the target boost. If not add more duty cycle. If yes remove duty cycle. Do another power run to confirm. When the duty cycle is about correct, you will make the desired boost level, with minimal over spiking. When you have determined the minimal duty cycle for your desired boost level, this will be your Progressive setting. Adjusting the duty cycle beyond this minimal point will bring boost on quicker, but with some spiking, a few percent more can make a big difference here and this is where the learning value comes into it's own. When boost spikes over the desired level, the learning value is adjusted, and after some time driving on this setting the ECU will learn to boost quickly with minmal spiking.

APEXi describe the value your after as a 'Learning Value', and it's normal to see it change as the boost controller adjusts it's own parameters to fine tune the solenoid. If the duty cycle is accurately set, then the learning value should change a litle over time, maybe to about 200. If the duty cycle is way off the mark, then the learning value will either be way low, say less than 50, or not reduce at all. In which case you could make some adjustment to the duty cycle to have better boost control.

Difficualt to say, as I made so many other changes at the same time, concensus is that there are better ways to spend your money. Yep, took quite a bit of work, though nothing too technical. Not hard, just time consuming and involves lots little modifications of different parts of the engine / engine bay.Biggest problem is getting the old plenum off, as it's a pain in the knuckles splitting the OEM plenum from the runners, and there are loads of bolts holding it to the cylinder head, and a multitude of pipes connecting the under side of it that you can't see. Then you need to build up the GReddy plenum with parts removed form the OEM plenum, and make a few modifications to the wirirng loom that the otherwise good GReddy instructions forgot to mention. And don't forget to add the cost of the inlet manifold gasket, loads of rubber hose, and the custom IC pipe work.

Lukevl, If it weren't for this continued bickering shite, we may have had an answer to the question by now. :upurs: Bugger this, I'm going back to my home forum, at least the bickering isn't personal over there :run: SK, I'd still like to discuss this even though it's purely academical on my part, as you know I've already made my choice of plenum. You're welcome on the register anytime dude

So, Lets get hypothetical then...... I've got an RB25DET, which has had a numerous modifications made to bring it up to the theoretical (mythical) 450bhp limit of the stock plenum, and I just happen to have at my disposal, an RB26 plenum, and a GReddy one. What do you see as the pros and cons of each in big power the RB25 application ?

Bloomin'eck, I hope that's not directed at me, I particularly respect SK's opinion, and have sought him out in the past as a mentor............ So SK, whadaya reckon ?

SK, I don't doubt for a second that the GReddy Plenum, in either RB25 or RB26 applications, only comes into it's own after a certain level of airflow is required, nor do I doubt that the OEM designs are good ones, but I'd still love to see the figures so as to appreciate just how futile the whole argument really is. Like BBQ though, I'd like to know your POV regards the RB26 plenum on an RB25.......