Rb25de+t Dyno

[lammy426]

take a look, any comments welcome,power fc,480cc injectors,fmic,modified plenum,oil cooler,255l fuel pump,air filter/pod,de-cat,de-cat back 3" to3.75"xs poer exhaust and kenlowe fan

[Dale FZ1]

Quite a reasonable outcome. Torque curve below 4500rpm would be more pleasing if it was filled out a bit more.

Stock 25DET turbo fitted? What boost level?

Sounds like the exhaust is relatively de-restricted too; noise levels not over the top?

There's a little bit of literature out there about high compression and forced aspiration that guides on effective static compression. Basic outcome is that there is a boost level at which your 10:1 engine will see a rapid increase in "effective" compression and head towards/over the detonation threshold. Be careful if you want to push further.

[lammy426]

Quite a reasonable outcome. Torque curve below 4500rpm would be more pleasing if it was filled out a bit more.

Stock 25DET turbo fitted? What boost level?

Sounds like the exhaust is relatively de-restricted too; noise levels not over the top?

There's a little bit of literature out there about high compression and forced aspiration that guides on effective static compression. Basic outcome is that there is a boost level at which your 10:1 engine will see a rapid increase in "effective" compression and head towards/over the detonation threshold. Be careful if you want to push further.

8.5psi but i've added a turbo elbow downpipe,tubular manifold and splitfire coilpacks and thats it i'm hoping i have not got to lower the boost as it will raise up

[r33cruiser]

thats pretty respectable.

im a bit picky. but i would try to get that torque curve smoothed out.

p.s. bloody good work on the intake manifold. never thought of doing that. saves $1000+ when u dont need a greddy plenum

[Fat_Tony]

Looks dodgy to me. Still using the stock intake runners, which are designed to take the feed from the middle of the plenum.

[l0WRB]

indeed, specially wen u can bolt up a knock off greddy item for 500bux:)

[dano4127]

plenum mod would have cost $500 if it was done "properly" a mate of mine paid nearly $800 which I think was a little extreme

[STATUS]

thats pretty respectable.

im a bit picky. but i would try to get that torque curve smoothed out.

yeah but remmeber this is a dynapack dyno which gives different looking graphs, more emphasised than DD they are more sensitive... in a good way. Hence why i ordered one

p.s. bloody good work on the intake manifold. never thought of doing that. saves $1000+ when u dont need a greddy plenum

yeah its actually not great, in this application it will suffice but we flow tested and thermo-coupled a couple and there is a huge variance in flow to cyls 1 thru 6... a big differrence. there is just no real way of doing it properly, without going to another top half or complete plenum.

[r33cruiser]

wow ok uras i believe u. i stand corrected.

now im really glad i forked out for a greddy plenum

[R34GTFOUR]

thats pretty respectable.

im a bit picky. but i would try to get that torque curve smoothed out.

p.s. bloody good work on the intake manifold. never thought of doing that. saves $1000+ when u dont need a greddy plenum

i doubt that torque curve could get much better. Most of the de+t setups have all the timing ripped out down low to help it stop pinging when its coming onto boost because of the cr.

Not a bad result though

[lammy426]

yeah but remmeber this is a dynapack dyno which gives different looking graphs, more emphasised than DD they are more sensitive... in a good way. Hence why i ordered one

yeah its actually not great, in this application it will suffice but we flow tested a couple and there is a huge variance in flow to cyls 1 thru 6... a big differrence. there is just no real way of doing it properly, without going to another top half or complete plenum.

theres lots of these plenums over here with no probs,and theres no way you would get as much power from it as you would a greddy one because its only got a standard throttle body,i have got a greddy type one but theres no point in using it until i lower the cr or blow it up and put a rb25det engine in it or if i smash the car i'll just buy a gtst and swap the bits over and in the meantime its all fun

[lammy426]

Looks dodgy to me. Still using the stock intake runners, which are designed to take the feed from the middle of the plenum.

when under boost the whole plenum is pressurised and not all intake valves open at once these intake runners are designed to suck not have air forced in them,i've heard on a forum somewhere theres been tests on these mods and the greddy one only took over at high bhp can't remember what the figure was or where it was but this engine will never get great figures with a high cr,ah and it costs nothing to do if you know a welder

[Dale FZ1]

Check out this little guide

High compression forced aspiration cars are a little (lot) more fussy when it comes to making them detonation proof. That high effective static compression ratio indicator shows that a 10:1 engine will probably take a LOT less timing across the entire range of on-boost load. So in some respects what's being gained through the compression is being lost through comparatively retarded timing when looking at the 9:1 DET spec.

i doubt that torque curve could get much better. Most of the de+t setups have all the timing ripped out down low to help it stop pinging when its coming onto boost because of the cr.

That's what it is all about.

and in the meantime its all fun

I agree, and while it may lack a bit of the bling etc, if it works effectively and you suffer no driveability or reliability at this level of tune then run with that manifold setup. Not how I would do it, but that's just my view.

this engine will never get great figures with a high cr,ah and it costs nothing to do if you know a welder

FWIW, below is a graph of my DET with light mods and small-spec high flow. 300hp, with boost peaking at 13psi and tapering to 12psi. If you have 10 minutes, plot the points from one graph to another (yeah, I know, not directly comparable...) but you can pretty much see the difference. Same sort of max power number, but the 9:1 engine has bucketloads more from 3200-5800 where you drive it.

That is a function of the mass flow capacity of the turbocharger at differing pressure ratios - the high comp engine just won't let you pump too much in before it reacts with knock.

Hope that adds constructively to your setup and understanding differences.

[lammy426]

Check out this little guide

High compression forced aspiration cars are a little (lot) more fussy when it comes to making them detonation proof. That high effective static compression ratio indicator shows that a 10:1 engine will probably take a LOT less timing across the entire range of on-boost load. So in some respects what's being gained through the compression is being lost through comparatively retarded timing when looking at the 9:1 DET spec.

That's what it is all about.

I agree, and while it may lack a bit of the bling etc, if it works effectively and you suffer no driveability or reliability at this level of tune then run with that manifold setup. Not how I would do it, but that's just my view.

FWIW, below is a graph of my DET with light mods and small-spec high flow. 300hp, with boost peaking at 13psi and tapering to 12psi. If you have 10 minutes, plot the points from one graph to another (yeah, I know, not directly comparable...) but you can pretty much see the difference. Same sort of max power number, but the 9:1 engine has bucketloads more from 3200-5800 where you drive it.

That is a function of the mass flow capacity of the turbocharger at differing pressure ratios - the high comp engine just won't let you pump too much in before it reacts with knock.

Hope that adds constructively to your setup and understanding differences.

is that bhp at the hubs or the fly,and i see what you mean about the graph and thanks but i'm still going to see if it'll go to 12psi and in the meantime i'm looking at buying a gtst engine to rebuild,and whats your opinion on water injection,thanks john

[Adriano]

With a hood water/meth injection system, 12 psi should be a really good thing, better than a DET with the same setup. The dyno graph comparison only shows half the story, as your motor should make more torque than the DET when not at full throttle, and return better equivalent fuel economy.

[Dale FZ1]

Agreed. WI would be very highly desirable (essential) if you want to run to higher boost levels and keep the thing away from knock. That then places a big demand on system reliability, and fail-safe protection. Some systems offer flow blockage indicators and boost control interface to help keep things safe if you do encounter water flow failure.

The off-boost torque, and potential fuel economy difference is definitely a +ve for this configuration, but it's worth grasping the whole picture for high comp + forced aspiration. You might make another 20 or 30 rwhp with higher boost, but pushing it towards the edge of sensible limits. Getting really good results beyond that 300hp is going to take some thought and careful tuning. I've looked very carefully at the 25DE piston design, and my opinion is that there are some little sharp edges around those valve cut-outs that are not knock-friendly.

The other issue I'd be aware of is what Nissan did NOT put into the DE - oil squirters under the piston, and the dinky oil heater/cooler. They obviously felt it necessary to do something to remove heat from the piston crowns in the DET version in the name of reliability. WI would take care of that to some extent, but just be wary if you pushed the DE+T too hard, too long. Very good streetable combination, but you'd need to know where its weaknesses are when leaning on it for more.

Edit: that dyno sheet shows power at the wheels.

Edited February 7, 2008 by Dale FZ1

[Fat_Tony]

when under boost the whole plenum is pressurised and not all intake valves open at once these intake runners are designed to suck not have air forced in them,i've heard on a forum somewhere theres been tests on these mods and the greddy one only took over at high bhp can't remember what the figure was or where it was but this engine will never get great figures with a high cr,ah and it costs nothing to do if you know a welder

It doesn't "look" like it would flow evenly. Don't have any evidence to back it up.

It would be good if it does because I've been looking for a cheap set-up with shorter intercooler piping.

[lammy426]

It doesn't "look" like it would flow evenly. Don't have any evidence to back it up.

It would be good if it does because I've been looking for a cheap set-up with shorter intercooler piping.

nothing to back it up but theres a few over here been running them for years with no probs and a greddy one looks like its got less volume in it,theres no doubt the greddy is better mainly because you can fit a bigger throttle body

[GeeTR]

Plenum's with I6's are bout flow equality, not outright MASS, IMO

The fact ppl are using modded stocky's to make a lot of power and reliably is simply an indicator to me they're loosing a deal of power having to tame fuel & ignition to suit the lowest cylinders det threshold.

As URAS said, with these modded stock manifolds, you really would need to trim each cylinder with thermo couples / WB sensor... to get the best from it.

High comp and boosted setups require v.good manipulation of cyl pressures, assuming you dont cheat and use WI hahahaha jk.

Good result John

[STATUS]

Well put ^^^