Jump to content
SAU Community

Recommended Posts

Just thought I would throw this in, Mate of mine is doing up a VL with the RB30/25 Conversion. He is running standard rods in it but some how he got his hands on some nissan motor sport forged piston's that weren't available to the public!!!! lucky prick. He is running a custom turbo flowing 600Hp at 6psi. The engine is complete and is about to have my other mate make the inlet and exhaust manifolds up for him. Tremic 5 speed rated to support 600Hp. 750cc injectors. He was tossing up his options between power FC or a Link computer and after talking to his tuner is going for the Link due to being able to remove the AFM. should be a pretty good car when it's complete.

You sure about that?

My head flow's pretty bloody well and I've got high flowed T07S (650-700hp turbo), and my car needs 3 times the amount of boost to flow that.

I think your mate is telling fibs.

BTW - a turbo doesn't flow 600hp @ whatever PSI. An engine running a turbo @ whatever psi may produce 600hp. A turbo is just an air pump! :D

Oh - and PS - Don't discount the PowerFC just because you have to run an AFM! My car's running one and I don't have any issues with it! Cold start is perfect out of the box, bolts straight in without modifying the harness, it's very easy to tune, and a most of the part throttle maps only need a bit of tweaking vs. creating from scratch on a Link ECU. Plus it's a 20x20 map for inj & ign!

matt

He is running a custom turbo flowing 600Hp at 6psi.

Hi Mat, the rule of thumb says 600 bhp = ~66 lbs of air per minute. Then all you need to do is look for a compressor map that shows that amount of airlfow at ~6 psi.

The T76 looks likely;

t76%20turbo.jpg

Yep, ~65 lbs of air per minute at 1.5 pressure ratio (7.3 psi).

So, I have no problem with claim from the "mate of awurths", except he must be crazy. Why would you use a 900 bhp + turbo to make 600 bhp? The lag would be obscene, not to mention the piss poor turbo efficiency (~60%).

But, hey it could (theoretically) be done, I just don't know anyone that silly.

I'm not a mechanical genius but one of the first things i got my head around is that everythings to do with flow rates. I'm not dumb, I understand that just cause the turbo can flow that amount of air doesn't mean the motor will produce it. That all comes down to other factors within the motor and tuning. That is beside the piont.

A bit more on that VL. It is in Mackay, Qld. He bought the turbo off a guy in Mackay who had it made up for his Gen III ute, so yes I don't think the compressor efficiency would be desirable on the VL. He is basically running it cause he got the turbo and external Wastegate fairly cheap. He is running different cams (lift and Duration??? but they seem fairly aggressive when compared to normal turbo one's) He has gone for a Link because the turbo has a 4 inch inlet and he really doesn't want the restriction of an AFM, the link is closed loop as well, so that will be very helpfull. the tuner also likes the software with the link (not getting into arguements, I think PowerFC's are great and am considering one for my GTR with RB20 AFM's). I too reckon the power delivery will fairly late and fairly sudden and his clutch will be screaming for mercy after not too long. at least the engine bay will look good with this HUGE turbo sitting there!!!!!

I know you guys would probably want more specific info about it so i will try find out more later and post it.

Hi Mat, the rule of thumb says 600 bhp = ~66 lbs of air per minute.  Then all you need to do is look for a compressor map that shows that amount of airlfow at ~6 psi.

The T76 looks likely;

t76%20turbo.jpg  

Yep, ~65 lbs of air per minute at 1.5 pressure ratio (7.3 psi).

So, I have no problem with claim from the "mate of awurths", except he must be crazy.  Why would you use a 900 bhp + turbo to make 600 bhp?  The lag would be obscene, not to mention the piss poor turbo efficiency (~60%).

But, hey it could (theoretically) be done, I just don't know anyone that silly.

How do you read that Graph? What would be a good example of what kind of pressure I need to run with the GT30/40 turbo to get 500HP or so?

GTR-Ben, the airflow across the bottom is straight forward, on the vertical axis is boost pressure - this is absolute pressure, so you need to subtract 1 from the value to get boost that is seen in the manfold

- absolute pressure is the total pressure, including the atmospheric pressure which is 1 bar, thus it needs to be subtracted.

So, drawing a line up from any given airflow point, you can read boost required off the vertical axis, and where in the efficiency map the compressor is working. The line to the left of the map is the surge line.

He has gone for a Link because the turbo has a 4 inch inlet and he really doesn't want the restriction of an AFM

Hi awurth, tell your mate that the car below has AFM's, it makes 1,000 + bhp, runs the 1/4 in 8.4 at 165 mph. Not much of a "restriction" it would seem. BTW it uses a Power FC as well.

The "AFM = restriction" is a myth, you just have to have the right sized one for your application. Spread the word.

A bit more on that VL.  It is in Mackay, Qld.  He bought the turbo off a guy in Mackay who had it made up for his Gen III ute, so yes I don't think the compressor efficiency would be desirable on the VL.  He is basically running it cause he got the turbo and external Wastegate fairly cheap..

Hi awurth, if he got it "cheap" then he could sell it and make some money to buy the right sized turbo. A turbo spec'd for a 5.7 litre pushrod, 2 valve per cylinder V8 is hardly ever going to work on a 3 litre, DOHC, 4 valve per cylinder 6. He should be able to sell the "big" turbo and buy an equally used "smaller" one and have money left over to buy other go faster bits.

Pass that on to "your mate", take it from someone who has tried it. There is no way of overcoming a mismatched turbo, if it's spec'd wrong, it's always going to give a less than desirable/possible result.

SK if you were to use a RB26 head on the RB30 in a R33 gtsts would you use the loom in the engine from the RB26 and then run a RB26 power fc with twin afm, or is there a way to run twin AFM with the rb25 loom

Hi Buster, yes you can run 2 X AFM's with the RB25 loom, but it really goes back to why do you want to run 2 X AFM's?

Hi Gary, you once quoted

1 X RB20/25 AFM = 370 bhp = 220 rwkw

1 X Z32 AFM = 420 bhp = 260 rwkw

2 X RB26 AFM's = 475 bhp = 300 rwkw

2 X Z32 AFM's = 700 bhp = 470 rwkw

1 X Q45 AFM = 480 bhp = 300 rwkw

2 X Q45 AFM's = 850 bhp = 550 rwkw

I was planning on running 2 x Z32 AFM's and a power fc pro, I was using one Z32 with my old set up and made 330rwkw but am hoping for a touch more power then that with the new set up which makes me think i'll be needing to use 2 AFM's if I use power fc

Wow Buster, that's an old post. We are almost up to 400 rwkw with a single Q45 AFM now. This Apexi drag car (below) with the 2 X Q45 AFM's making well over 1,000 bhp prompted me into trying for more out of the single Q45. We have not seen any measurable restriction so far. Plus you proved the Z32 AFM 260 rwkw rule of thumb to be out of date with your 330 rwkw.

You can parallel up a pair of AFM's and use them with a GTST ECU, they need to be exactly the same though. Give me a call an I will run you though the process, bit too tricky to do via the keyboard.

I am working on updating the table in light of these and other recent testing results. I will post it when I am confident in using them as a new rule of thumb.

The more you test and push the envelope, the more you learn.

SK: how strong is the crankshaft and what aftermarket options are avail?

If you mean the RB30 crank, I have seen 900 bhp using a standard crank. We are just about to build one with 1,200 bhp, give me a few months and I will be able to tell you whether or not that is the new benchmark.

As for aftermarket options, well there are lots of choices. Almost every Australian and NZ machine shop has the capacity to make a forged RB30 crank. Add a large number of the US majors to that and you have plenty of choices. Both standard stroke (85 mm) and long stoke, I have seen up to 94 mm stroker cranks for RB30's.

Hope that helps

Ok it may be getting off the whole RB30 thing, but why do you keep the AFM's Sydneykid? Do they allow for easier tuning?

I have a Linkplus ECU all wired into a GTR loom for use with my RB30 with the GTR head. It is setup to use no AFM's.

HiBen, some people prefer to use MAP's sensors, some prefer AFM's, I just happen to believe that Skylines run nicer on AFM's. I'm not saying that they make more power, or go faster, or use less petrol, or cost less. What I am saying is, for equal power, an AFM equipped Skyline, in all atmospheric conditions, will generally run nicer than a MAP sensor only equipped Skyline. I like my cars to run nice all the time, it's a lot harder than simply making lots of power.

As for Link ECU's, as far as I know they don't work with AFM's, so you have to use MAP sensors for engine load readings.

hey guys,

anyone looked into the safe RPM limit of an RB30?

I have spoken to someone who said that anywhere over 6600rpm is asking for trouble. I was looking at using a 7000rpm limit, but was told i would be treading lightly on reliability.

any info?

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



  • Similar Content

  • Latest Posts

    • I came here to note that is a zener diode too base on the info there. Based on that, I'd also be suspicious that replacing it, and it's likely to do the same. A lot of use cases will see it used as either voltage protection, or to create a cheap but relatively stable fixed voltage supply. That would mean it has seen more voltage than it should, and has gone into voltage melt down. If there is something else in the circuit dumping out higher than it should voltages, that needs to be found too. It's quite likely they're trying to use the Zener to limit the voltage that is hitting through to the transistor beside it, so what ever goes to the zener is likely a signal, and they're using the transistor in that circuit to amplify it. Especially as it seems they've also got a capacitor across the zener. Looks like there is meant to be something "noisy" to that zener, and what ever it was, had a melt down. Looking at that picture, it also looks like there's some solder joints that really need redoing, and it might be worth having the whole board properly inspected.  Unfortunately, without being able to stick a multimeter on it, and start tracing it all out, I'm pretty much at a loss now to help. I don't even believe I have a climate control board from an R33 around here to pull apart and see if any of the circuit appears similar to give some ideas.
    • Nah - but you won't find anything on dismantling the seats in any such thing anyway.
    • Could be. Could also be that they sit around broken more. To be fair, you almost never see one driving around. I see more R chassis GTRs than the Renault ones.
    • Yeah. Nah. This is why I said My bold for my double emphasis. We're not talking about cars tuned to the edge of det here. We're talking about normal cars. Flame propagation speed and the amount of energy required to ignite the fuel are not significant factors when running at 1500-4000 rpm, and medium to light loads, like nearly every car on the road (except twin cab utes which are driven at 6k and 100% load all the time). There is no shortage of ignition energy available in any petrol engine. If there was, we'd all be in deep shit. The calorific value, on a volume basis, is significantly different, between 98 and 91, and that turns up immediately in consumption numbers. You can see the signal easily if you control for the other variables well enough, and/or collect enough stats. As to not seeing any benefit - we had a couple of EF and EL Falcons in the company fleet back in the late 90s and early 2000s. The EEC IV ECU in those things was particularly good at adding in timing as soon as knock headroom improved, which typically came from putting in some 95 or 98. The responsiveness and power improved noticeably, and the fuel consumption dropped considerably, just from going to 95. Less delta from there to 98 - almost not noticeable, compared to the big differences seen between 91 and 95. Way back in the day, when supermarkets first started selling fuel from their own stations, I did thousands of km in FNQ in a small Toyota. I can't remember if it was a Starlet or an early Yaris. Anyway - the supermarket servos were bringing in cheap fuel from Indonesia, and the other servos were still using locally refined gear. The fuel consumption was typically at least 5%, often as much as 8% worse on the Indo shit, presumably because they had a lot more oxygenated component in the brew, and were probably barely meeting the octane spec. Around the same time or maybe a bit later (like 25 years ago), I could tell the difference between Shell 98 and BP 98, and typically preferred to only use Shell then because the Skyline ran so much better on it. Years later I found the realtionship between them had swapped, as a consequence of yet more refinery closures. So I've only used BP 98 since. Although, I must say that I could not fault the odd tank of United 98 that I've run. It's probably the same stuff. It is also very important to remember that these findings are often dependent on region. With most of the refineries in Oz now dead, there's less variability in local stuff, and he majority of our fuels are not even refined here any more anyway. It probably depends more on which SE Asian refinery is currently cheapest to operate.
    • You don't have an R34 service manual for the body do you? Have found plenty for the engine and drivetrain but nothing else
×
×
  • Create New...