Forum » General Tuning Discussion » Rb25 boost

Rb25 boost

General Tuning Discussion

Discuss all things tuning in this section. News, products, problems and results. 


Page 1
Author
145 Views

Hey guys ive built an rb25 engine from an r33. I used wossner forged pistons and pec rods. It has stock compression ratio, solid lifter conversion and running hks 256/264 cams, inlet vct is still functional. The car has 2x bosch 044 pumps, twin feed rail and id1300x2 injectors. Turbo is a 6062 gen2 precision. The car will be used for drifting. It is running on e70 fuel mix. Can anyone advise a rough target for max boost pressure?

It's a difficult question to answer as the boost will come down to your power targets and the way the engine will be used. For drifting you have the advantage that the engine is generally only under heavy load for the judged section and hence this is a relatively short time but boost and power generate heat and this needs to be managed.

The 6062 is a 750 hp turbo but sadly we don't get compressor maps for these turbos which isn't overly helpful. If you want the most out of the turbo you're probably going to need to be running in the vicinity of 30+ psi however this may be a touch high for long term reliability. I'd personally be aiming for a slightly more conservative boost level in the mid 20's which should provide a good mix between reliability and power. Ultimately only you can decide where you are comfortable on this scale though.

Went up to about 30psi positive boost pressure when mapping, it made 625hp, the car comes onto boost very quicky, but as it get higher in the rev range it fails to make more power, even with adding a little more boost, i think the exhaust housing on the turbo is too small, egts do start to climb a little high at higher rpm

had the car on track today. there was a miss under throttle a few times, never noticed a miss on dyno.I have attached a link file and a log of a lap to see if anyone can give me pointers as to where I might be going wrong. Fuel pressure,egt and ethanol content are logged

Attached Files

You're misses are oil pressure related, the ECU runs into one of your GP limits. So at some point you're at high revs and your oil pressure drops below your threshold set in the GPLimit table. This happened quite a few times throughout the log.

You should really do something with your oil sump and pickup, possibly even go drysump depending on the g forces you're pulling during a drift.

Also, I've seen you're running the LinkECU in traditional injection mode whilst having an ethanol content sensor connected, which basically does nothing other than the value beeing logged.

I'd suggest properly tune it in the modelled fuel equation and make use of the sensor, or at least setting in up a 4D fuel table that compensates for ethanol.

Hi andy thanks for the help. Andy do you know of there is any way in the datalog time plot of showing the gp rev limit as a line graph alongside the oil pressure line graph as my gp limit has different pressures to meet at different revs. I can only get the oil pressure line graph. I know i could look back on the map to see but just for ease of use.

I have a winged baffeled and gated sump that holds nearly 4 litres extra oil with deeper pickup. I might take it off to see if something is wrong inside. Could anything else cause these issues?

I mix my own always e70 and just installed the sensor and have a look at it just incase i make a mistake in my mixing, however yes you are right i have a future road car project that i want to be able to use pump petrol too so for it i will try ethir 4d or modelled fuel.

Ah ive just noticied with link map file open and opening the gp limit table with the oil pressure timeplot running i can see the ghost cursor to show me where it hits the limits. My bad

Joseph, I usually log the GPLimits status to double check.

Well, it could be a wiring issue of the sensor aswell, but from the logs I'd say it is very likely to be indeed oil starvation.

In my experience your oil mods (baffles, oil capacity,...) do help a little, but at some point you just need to go with a drysump system.

On another note, there's the Accusump system, but we don't do that alot, so I can't really comment on its benefits.