DennisRB30

So I set my malpassi to 50psi base (referenced to atmospheric) Then had a look a week later and its at 30psi. My car was going VERY hard at that fuel pressure with wheelspin through first and second with 0.7bar. So I put it back to 50psi as I think it was at 50 when we tuned it. (I say THINK because I set it a few days before we tuned it and it may well have went down before we tuned it). After I put it back to 50 I went for a drive and the car ran like crap and was misfiring. So I checked it again and it was at 75psi base! I put it back to 50 again and it seems to be staying there now. WTF is going on?

Any in Brisbane?

Well yeah. Thats comparing 100 octane to 98 octane so that would be a given. I am talking about 98 octane E10 fuels like boost 98 from United servos.

Nice! So if you were running on the edge of detonation boost wise (23psi ), E10 will give you a safety margin over normal fuel? (providing AFR's are the same).

Any responses from tuners?

Was that E10 98 or E10 100? It would be sweet if you could find the article. Frost. Yeah it might chew a little bit more but it costs way less from united servos.

I am thinking of running my car on this fuel. I know it will make it run leaner per the same amount on fuel injected due to the oxygen content. Say I was running a 12.5:1 AFR with ultimate, what would it be running at if I swapped to E10 with no tuning changes? I'm just trying to get a rough idea how much more fuel flow I would require. After AFR's have been restored. Will it take more or less ignition advance than normal fuel?

I run an Auto with 4.1 gears. I actually changed them from 3.7. First gear still fries the tires. So it does NOT have the lag problem from low speeds you are talking about. So I would be silly to bother with a 0.82. Also your findings on the 0.5 building boost more gradually seems to oppose the dyno chart I provided where the 0.5 comes on much harder and the owner says its more of a tire fryer with the 0.5.

True. That's why lifting the rev limiter is an enormous help to average power when you use a large turbo. Looks like this guy might want a GT35 and the extra revs will help a a lot with average power since there will be a lot of lag in the mid range. I'm sure with that turbo selection he wants more than 250rwkw at some time in the future.

Yeah, fairly oversimplified, however I was only talking about comp AR's not rear housings. But I also linked to a real world example of a comp cover change on the XR6 site where the smaller cover seems to be much better over all than the larger one (well on an XR6 anyway). I don't know why the Garrett site only had that one small paragraph on comp covers when the site goes into a lot of technical detail in other areas. Seems most of the RB30DET guys are getting a lot more lag with 0.82 rears than I am with a 1.06 rear and 0.5 front. I get 15psi by 3500rpm in second gear with a $200 ebay manifold (auto) probably equal to 3rd gear with a manual. According to the XR6 thread I linked to, the smaller front gives a LOT more response. Most people just ignore the front cover, or just get the biggest one possible when that may not be the best option. I'm just trying to get people to take notice of the front cover as it may have a bigger effect of the power curve than what they are led to believe. From XR6 site. Chart is 0.5 front VS 0.7 front. As you can see it has MUCH better mid range power with some power loss in the top end, however it was running 2 psi less in the top end, and they reckon once they up the boost to where it was with the 0.7 it will "cream" the 0.7 there too. This is only one comparison and its on a 4 litre engine, but its enough to make you think twice about comp cover selection.

Food for thought on the front cover 0.5 VS 0.7 Everyone just seems to ignore the front cover and only worry about the turbine housing. Check this out. The smaller front may actually be better for average power. http://www.fordxr6turbo.com/forum/index.php?showtopic=32271 According to Garrett, the smaller front cover has a very minimal effect on power, and smaller AR's are actually better for higher boost levels. So I think I am on a winner with the 0.5 front. I was going to change it but I am not now. I think it might be better! http://www.turbobygarrett.com/turbobygarre...bo_tech102.html

If the lid opens you cam make a divider in it.

People always stuff this up. Here is one solution.

Anyone got pics of these plenums? Do they just use the stock bottom half joined to a sheet metal plenum chamber? I don't like the way power is only shifted toward higher RPM without actually increasing it. Sure, you get more high RPM power, but you loose it in the mid range. You would get the same on road feel at similar speeds by fitting taller gears.

The big ones.

Do you know of the FB speed effects the opperation of the unit?

At the end of the day I can show you some 2JZ graphs with 380rwkw with this turbo. A 650-700 horsepower turbo is going to need to expel 650-700hp worth of gas when pushed to its limits regardless of engine size (as long as the engine is large enough max out the turbo) Its the turbo which limits this not the engine. All that will happen on a larger engine is it will choke the larger engine sooner. Supras pick up huge power gains when swapping to larger exhausts from 3". I can't see why a similarly developed RB30DET would be different. Yes you can make good power with a 3", but if you are making good power with a 3" you will see great gains when you go larger. I'm talking over 300rwkw here. An XR6 has an exhaust equivalent to larger than 3" STOCK! Since its fairly large you can make great power though it, but it starts to limit power after 300rwkw.

Not as easy as that. A 4 litre running say 350rwkw is going to have a similar amount of exhaust gas as a smaller engine running 350rwkw. The smaller engine may need more boost and revs. But over all exhaust gas flow will be similar. The 4 liter might make 350rwkw @ 5500rpm on 17psi but the 3 liter might make the 350rwkw at 7000rpm at 23psi. The overall turbo size will be more reflective of how much potential exhaust flow an engine will require than the actual size of the engine.

All the XR6 guys will agree that 3" is too small on thier cars with the stock GT35 that comes on the XR6. They all get good power gains by going to 3.5" preferably 4" exhausts. I have a 3.5" dump and the rest is 3.1" which I think will limit my power with this turbo.

It frys the tires in first gear and makes 1 bar by 3500 in second so that is certainly not the case with my setup. I have 4.11 gears also. But, yeah the taller gearing of the auto does help it spool a bit quicker. I was worried about lag but its not laggy at all. Another mate has a GT35 1.06 IWG with the 0.7 front on his manual VG30 R31 and its not laggy either. Must just be some prob with the RB30DET's. Plenum maybe? Or just mismatched gears that were meant for high revving engines. I think some of the guys with manual RB30DETs need to change their diff gears to suit the power delivery of the engine. 4.3 gears with a manual are not going to load it up enough in a light R32 or similar. I know someone who fitted taller diff gears which made the car much quicker since the turbo actually built boost in low gears.

I have 044 which I mounted in my R31 fuel tank on the stock bracket. Its quite noisy. I'm not sure if its my 044 which is at fault if its vibrating the bracket and causing the noise. You can hear it more from outside of the car than you can from inside though. It doesn't really bother me. I never used a surge tank and it would surge at 1/3 tank under acceleration. I fixed this with my dog food surge can mod. Some say dodgy, I say less dodgy than an expensive, illegal, smelly and space taking surge tank in the boot. It works fine I have no surge issues at all now. Some shitty pics.

I just put a used XR6 GT35 1.06 rear on my 2JZ powered R31 with a $200 ebay manifold. The 2JZ has the same bore and stroke to a RB30 and with the twin cam head should be quite a similar engine response and power curve wise. 2JZ's plenum's are not restrictive so that would probably be the major difference. My engine is stock, with stock ECU and stock auto trans etc, it has a 3.5" dump and 80mm exhaust with ebay 100mm cooler. I am yet to put it on a dyno but it feels a lot stronger at 14psi than my old stock twin setup did at 20psi, which was dynoed at 241rwkw at 15psi. I can get 1 bar of boost up by 3500rpm in second gear, so its quite responsive given that it has the larger rear housing. Guys on the supra forums are getting 500rwhp with this turbo, some even with the .82 rear. I have no idea what RB30DETs should be putting out but that gives you a basis for response and power comparison on a similar spec engine. Maybe Cubes is right about the plenum?

Its used. The duty at 6000 is zero since it boost spikes to 1 bar in the high RPM anyway. This is due to my internal gate being too small. Duty is 90 from 0-4000. Makes 1 bar by 3500. I then taper the duty down sharply toward zero from 4500-6000rpm. The idea being to get 1 bar as quickly as possible without getting more than 1 bar by redline. Setting the duty up like this should have worked from the beginning, but one of the other features must have been stuffing with it. Maybe the FB speed was causing the inaccuracy with the RPM mapping?

I turned all the features off or to zero. This fixed the prob. The RPM mapping seems to work again now.

Why would having a high duty at low RPM cause overboost at high revs where the duty is set to minimum?