Your opinion, more boost or not? RB25DET GTX3076R

[Aleckr33]

Your opinion, more boost or not? RB25DET GTX3076R

G'day guys, I'm after your opinion or anyone that has a similar setup to my car.

Car is a 1998 R33 GTS25T

Current mods

Stock bottom RB25det, compression 150 - 160 across all 6.
Stock head gasket
ARP head studs
upgraded valve springs
camtech 272 9mm cams
Haltech plat pro
wideband kit
3 bar map sensor
6boost t3 twin scroll manifold
garrett gtx3076r .83 twin scroll, 50mm external gate
Walbro 460 e85 intank fuel pump

Currently making 
336rwkw @ 19psi low boost
360rwkw @ 25psi high boost
United E85 fuel

Before i go and speak to my tuner i wanted to ask you guys....
Has anyone thrown in more boost with a similar setup? Should i leave it where it is? looking at turning it up to 28-29psi to hopefully crack 400rwkw or close to.

Cheers.



 

[KiwiRS4T]

360rwkw sounds pretty good but more may be possible. I would just ask the tuner to keep increasing boost until 

1. EGTs get too high or

2. detonation approaches or

3. It stops making more power.

 

 

[Kinkstaah]

I've had that setup on a RB28. Yes it can make 400 at that boost.

Just leave it as it is, man. It won't really make the car any faster in 97.7% of scenarios. Why tempt fate? I'd go as far to say as leave it on 19psi with a stock gasket. Twin scroll housings and manifold should make it a pretty potent setup.

Source: Tempted fate.

[ltcree]

I made 413 on 30psi with a built motor, there's still a little more in it but we are blowing out the spark.

[Borci88]

Well to put it into perspective, you gained an extra 24kw by bumping it up an extra 6psi. You now want to make it crack 400kw, an extra 40kw by only going up another 4-5psi. 

Logically that ain't gonna happen if the tune was done well in the first place. Can always give it a go and it might happen, but I think its optimistic.

[rx-line]

I wouldn't be going past 25psi, typically stock rings are not meant for such high cylinder pressures. Especially in an engine known to have ring land issues In theory you would no want the rings to touch and compress on one another. I'd be looking at other items rather than boost pressure to hit 500hp.

 

In my RB20 this year I did about 12 runs in a weekend at our local strip. I was upping boost constantly and ran a 10.67 twice with 25psi @ 131mph and 27psi @ 133mph (Different 60 foots). I then proceeded to run 29psi and 30psi. The engine still works "fine" and is fully standard stock internals, however it has a fair amount of blow by and I suspect piston failure due to cylinder pressures. 

[Aleckr33]

Thanks for your input guys. Another question for you...........

Closed loop vs open loop boost control

Since i use a haltech platinum pro ECU, is it better to control the boost pressure going through this ECU instead of using a EBC? Currently running off a Greddy ProfecB Spec II, which in my opinion doesn't feel like it is setup properly. What is better?

Cheers.

[KiwiRS4T]

I vote for ECU control. My car with Link, Mac valve and Synapse 50mm wastegate (and tuned by Soichi):

 

 

[admS15]

I also vote ecu. Mine is an adaptronic running a mac valve on a internal gate setup and the boost graph looks very similar too kiwis above.

[Aleckr33]

Wow that look's great. Right i knew this was the right way to go when i got the work done. So correct me if i'm wrong, If im using a EBC such as the profecB II. What is the use of the 3 bar map sensor i purchased with the Haltech ECU? Is it only used if i run the boost through the haltech?

[GTSBoy]

Um....the MAP sensor is your load input to the ECU.  It's how the ECU knows how much air flow is going through the engine (indirectly, by speed/density, rather than measuring it directly with an AFM like the factory ECU did).

[Aleckr33]

Thanks for that mate, So does this mean i am using that 3 bar map sensor with my Profec B II & ECU?

[KiwiRS4T]

Your MAP sensor is measuring airflow for timing and fuelling purposes. If you want your ecu to control boost you need to ditch your Profec EBC and get a Mac valve.

[GTSBoy]

Actually, the Profec has a MAC valve and the ECU could just as easily control that as any other.

OP.  The Profec has its own MAP sensor built in, which is how it knows what the manifold pressure is.  Not that it matters, because these boost controllers ARE NOT CLOSED LOOP.  They do not try to keep the boost in the plenum at a fixed value.  They just run the bleed valve at a pulsed duty cycle that is fixed when you set it up and for all time afterwards.  The boost measured by the Profec is just displayed on the front of it so you know how much you're running and so you can set it up.

If you use the ECU for boost control, then the ECU knows what the manifold pressure is from the 3 bar sensor you connected to it. 

Edited January 6, 2017 by GTSBoy

[Dose Pipe Sutututu]

Add more boost.. ring lands won't blow if you limit torque. Also spray more fuel at peak torque to keep the cylinder temperatures down and pump in more timing as torque decays..

I think the excess cylinder temps cause the rings to expand then smash the ring lands not so much the pressure/force.

Because you even hear of people smashing ring lands with cars making 250kW.

To put things into perspective, I've been thrashing the shit out of my car with about 1.8bar through the motor on the track and it's yet to go boom LOL... but like I said, I run very low timing at peak torque and spray heaps of fuel to the point it is about to misfire... but, the car is happy and the only thing that has died is the stock 300 000km head gasket and the turbo's arse end exploding.

[Aleckr33]

Thanks guys for all the info! ...  Has anyone had any experience controlling boost through a Haltech platinum pro ecu? Is boost more responsive & steady this way instead of using a EBC? I'm reading on other forums that haltech's inbuilt boost control is somewhat not accurate or tends to spike/overboost...

[rx-line]

2 hours ago, Dose Pipe Sutututu said:

Add more boost.. ring lands won't blow if you limit torque. Also spray more fuel at peak torque to keep the cylinder temperatures down and pump in more timing as torque decays..

I think the excess cylinder temps cause the rings to expand then smash the ring lands not so much the pressure/force.

Because you even hear of people smashing ring lands with cars making 250kW.

To put things into perspective, I've been thrashing the shit out of my car with about 1.8bar through the motor on the track and it's yet to go boom LOL... but like I said, I run very low timing at peak torque and spray heaps of fuel to the point it is about to misfire... but, the car is happy and the only thing that has died is the stock 300 000km head gasket and the turbo's arse end exploding.

Good point, progressive timing and rich fuel definitely helped my RB stay together for as long as it has. Heat is definitely the culprit in ring compression / failure, but the quickest way to heat is often cylinder pressure ( Boost, compression, nitrous, etc.) assuming everything else is fine?

More Air = More Fuel = More Pressure = More Heat, I think i'd be right in saying that.

1.8bar would be relative to the amount of flow, what turbo are you running?

[Dose Pipe Sutututu]

I'm running  (well was) the Hypergear SS2 with the ceramic BB centre, happen to be a prototype turbo too lol.. probably why it exploded when I ran stupid amounts of boost through it. The funny thing was it kept making power, so I kept adding boost.

You can control boost via the Halaltech very well if you've setup the base duty vs. boost target table correctly then enable the closed loop. I've done this on 2x cars already and boost control is fantastic. Of course there are a few tricks but a decent tuner should know what to do in terms of boost oscillation etc. but that costs dyno time, which workshops cbf spending time on.

[Kinkstaah]

+1 re: Haltech boost control (and Johnny's settings).

Really does work pretty damn well, unless you do weird shit like have an auto with a gate after the turbine wheel and load it up a hill. But that isn't Haltech's fault and it works really damn well, though I would wager most modern ECU's will. To be fair, I'd also say a standalone EBC can be setup to work just as well when you think about it, you shouldn't need to swap ECU's merely for the sake of boost control unless you want fancy things like Boost by gear, or Boost by XYZ variable that the EBC cannot provide.

[PatMol]

Sorry to jump in to the thread I have a similar setup I have been plugging at for 6 months.

Do you have a dyno graph?