The twin turbo setup

[Baz]

This is coming from someone who knows next to nothing about twin turbo setups.

Ok in a hypothetical situation where I designed a custom exhaust manifold to suit a single turbo motor such as a RB20DET or RB25DET which was designed to hold two turbos what problems would you have in running two turbos on a motor designed for one turbo?

Also some questions for the RB26 guys. If I had two turbos say with a limit of 200rwkw each would that bring with two turbos attached to the motor to 400rwkw's? Also if I had one turbo that had an actuator which allowed the output of the turbo to produce 15 pound boost, would a second turbo with the same specs bring the total turbo output to 30 pound boost?

Obviously there must be issues with this sort of setup on a single turbo motor otherwise it would be far superior to a single turbo setup and people would be doing it all the time.

[wrxhoon]

2 turbos = extra $ , stick to one its much cheaper .

2x turbos with a max 200 kw will give you a little less than 400 kw max.

2 turbos( or more for that matter ) pumping 15 psi each on their own , you still only have 15 psi .

[paulr33]

the internal gate actuator is connected in series (i think??) with the other actuator and they both share the same pressure line to the manifold or they run seperate lines but each have a 15spring actuator spring on them. so when the manifold goes above 15psi both actuator rods move at the same time and both int gates open. so you still only get 15psi max instead of 30psi.

i guess there wouldn't be many "issues" in going from single to twin or vice versa as long as you had a suitable manifold, water/oil lines etc. the ecu, fuel pump, shouldn't know any better. of course if going to single from twin then you only need one intake pipe, one afm and one cooler pipe, whereas going from single to twin, you need to add another afm, cooler pipe and intake pipe for the 2nd additional turbo.

single or twin turbo for RB26

http://www.skylinesaustralia.com/forums/sh...ead.php?t=72151

should give you some good background info as well

[GTRgeoff]

2 turbos = extra $ , stick to one its much cheaper .

2x  turbos with a max 200 kw  will give you a little less than 400 kw max.

2 turbos( or more for that matter ) pumping  15 psi each on their own , you still only have 15 psi .

1. Yep

2. Yep

3. Yep

Did the TT thing myself, great fun but complex.

[Baz]

Geoff, what turbos did you use? How efficient was your setup? Would you do it again? Expensive setup for the power/response created?

[R31Nismoid]

he is using 34 GTR turbo & manifold with an adapter plate made to suit.

[JaFF]

so what power is he making?

[GTRgeoff]

Actually the manifolds have been cut and welded then match ported to suit the 25 head. About 2500 for all of the parts not including labour as I did it myself. I'd expect it to come somewhere near 4K as a drive in drive out. I used braided lines and good quality fittings. I know I could do a similar job with a larger single but was impressed by the responsiveness of the car they came out of (Snowman) and wanted the novelty factor as well. It felt great and certainly would have been a bit sharper response wise from no boost than a 26 which has a lower compression ratio.

Unfortunately in the first drive something went wrong. I was just taking it onto boost the first time after idling it for an hour checking all connections etc. Had driven gently about 2km to the servo for air in the front tyres, left the servo, into second, clear road so started feeding the throttle. Got up to 5psi when it had a nasty miss kind of noise from the engine and by the time I backed off it had stopped, but was way down on power. I saw a cloud of brownish smoke in the mirror which I thought was fuel. Note that I had installed 440cc injectors as well. Compression is now down to 25psi on 1,2,3 and 125psi on 4,5,6 so well down on all. Discussion and analysis has led to the conclusion that the front turbine has let go, and is quite common on 26 turbos that have been removed and refitted. Whether something wasn't clean on install and came loose striking the turbine, or it was just their time I can't tell. I have to drop the front turbo to take a look.

As has been vaguely reported on the forum by others, it appears that when the ceramic turbine lets go it can suck back into the cylinders causing the bores to score and the valves to be held open by the particles. I myself have been a disbeliever of this phenomena but can see no other justifiable reason. The source of a lot of information on this is an identity that Ash would never think to question, even momentarily (a hint). I intend to dismantle and photograph as I go to nail this one for good if it is the causal element.

Also note that no blame is placed on Snowie. The turbos were bought and sold in good faith and good condition and could have lasted much longer if they had remained on his car. This is just one of those things associated with the ceramic turbine time bomb.

[R32 GT-R]

I think the biggest "issue" would be the response. It takes a lot more exhaust gas to spin up 2 turbo's you could make the same power just by bolting on a bigger single that would support the same power as the combined 2 turbo's hell you probably make a little more power.

[DivHunter]

That's why Craig Dean went for a big single on his Supra

[GTRgeoff]

Actually it won't. For response you use 2 turbos, for top power, a single as a rule of thumb, not that you can't make big power with the twins properly setup. The issue with the big turbo is the moment of inertia. There is a 3 page thread on it and as senior weapons systems engineer with years on turbocharged mechanical systems and gas turbines I'm comfortable with the theory and application. Basically the inertial difference can be a quarter for a small turbo compared to a similar power spec big turbo, all factors remaining the same due to the power functions influencing the calculation of the moment of inertia. I understand the actual theory but the proponents of the big single theory are yet to provide the fundamental theory for their claims.

[Sydneykid]

Hi Geoff, I have yet to see any evidence of ceramic in the engine disease on single turbo engines (RB20/25) but there are reports of it happening on twin turbos (RB26). I will be most interested in what you find when you pull yours down.

I understand the actual theory but the proponents of the big single theory are yet to provide the fundamental theory for their claims.

How about the weight of the rotating mass (compressor, shaft and turbine)? Some time ago I weighed the rotating components of a 2540 and compared it to a GT30. From memory 2 sets of 2540 rotating components would weigh around 1.6 times what 1 set of GT30 rotating components would. Hence would it not take 1.6 times the exhaust engergy (all other things being equal) to accelerate the compressor, shaft and turbine?

[Mik]

Hi Geoff, I have yet to see any evidence of ceramic in the engine disease on single turbo engines (RB20/25) but there are reports of it happening on twin turbos (RB26).  I will be most interested in what you find when you pull yours down.

How about the weight of the rotating mass (compressor, shaft and turbine)?  Some time ago I weighed the rotating components of a 2540 and compared it to a GT30.  From memory 2 sets of 2540 rotating components  would weigh around 1.6 times what 1 set of GT30 rotating components would.  Hence would it not take 1.6 times the exhaust engergy (all other things being equal) to accelerate the compressor, shaft and turbine?

That would only apply if the wheels' radii were equal. The reason for this is that rotational inertia is proportional to the square of the radius.

[GTRgeoff]

What Mik said SK. The moment of inertia (r^2 term) is calculated from the radius of gyration (r^4 from memory, I need to check) so the weight location from the centre of rotation is the killer.

I'll post a thorough report with pics when I find what went wrong, but the evidence is pretty indicative of a front "something" going bad as the only common thing there is the front turbo. As I said, I was an unbeliever. Thanks for taking an interest though mate.

[Ronin 09]

Is that why you're buying the rest of a twin setup then Geoff? i.e. an R33 GTR?

come join the darkside...

[GTRgeoff]

Just want 2 TT's mate. No way to debunk theories than to have RWDTT and AWDTT

No the GTR is my reward for being a good boy.

[wrxhoon]

What Mik said SK. The moment of inertia (r^2 term) is calculated from the radius of gyration (r^4 from memory, I need to check) so the weight location from the centre of rotation is the killer.

I'll post a thorough report with pics when I find what went wrong, but the evidence is pretty indicative of a front "something" going bad as the only common thing there is the front turbo. As I said, I was an unbeliever. Thanks for taking an interest though mate.

I have seen it with my own eyes , rear turbine let go and destroyed the rear 3 cil , pistons and bore scored , cil head embeded with the ceramic bits and a coulpe of valves bend .

I put pics up about 18 months ago , when i told SK he just wouldn't believe it was possible , he still doesn't .

When a ceramic turbo lets go in an rb 26 , some of the dust gets sucked in , sometimes very little other times heaps . Even if you check compression and its ok if you pull the engine out you will find some scoremarks in it .

[Sydneykid]

That would only apply if the wheels' radii were equal. The reason for this is that rotational inertia is proportional to the square of the radius.

Thanks Mik, I was aware of that, that's why I said "all other things being equal". One of the "other things" is the distribution of the mass from the axis. This is not something that is easy to measure. I can easily measure the diameter of the compressor and the turbine. But that may not give the answer as the profile of the blades is considerably different.

[GTRgeoff]

I have seen it with my own eyes , rear turbine let go and destroyed the rear 3 cil , pistons and bore scored , cil head embeded with the ceramic bits and a coulpe of valves bend .

I put pics up about 18 months ago , when i told SK he just wouldn't believe it was possible , he still doesn't .

When a ceramic turbo lets go in an rb 26 , some of the dust gets sucked in , sometimes very little other times heaps . Even if you check compression and its ok if you pull the engine out you will find some scoremarks in it .

Yeah, I still have trouble rationalising it, but as I said in a different thread some time ago, in fluid dynamics strange things can happen. The source of my info said it was possibly 1/3 that do it for 26's (that actually fail in the turbine). He does a lot of GTR stuff and is somewhat of a guru so I tend to be a little more believing of his experiences.

How's me for making the engine failure thread work though???? Just about doing it on my own. (oh stop it hurts)