Jump to content
SAU Community

Recommended Posts

Hey guys,

Got a quick question.

We were on the dyno the other night with my mates 32, we upped the boost from 1.1bar (strong, flatline 1.1 with no dropoff) to 1.4bar had a nice increase in torque and power (around 220kw) but, after boost ramps up nicely to 1.4, it slowly drops all the way to 1.1 by redline. Its as if the turbo is running out of puff.

Currently running a HKS 2530 63T with 0.64 housing, Tomei 260 cams (timing unknown at this point, but EX looks to be retarded for nice midrange judging by the CAS), HKS Adjustable actuator adjusted to achieve 1.4 bar with no bleed off, PowerFC. We previously had a mech bleed valve with actautor set to 1bar, did the same thing.

After viewing plenty of RB20 dyno sheets it seems common that people have boost drop across the revrange, so im betting on an EBC but just thought id get some input cos theyre not exactly cheap.

Must we run a EBC to control the boost? Im doubting it but could it be the cam timing affecting the boost so dramatically? Should we '0' the cams? Theyre the only other thing untouched.

Cheers!

Mat.

  • Replies 40
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Posted Images

I dont know much, just curious, but did i read correctly, that when the wastegate is adjusted the issue goes away? ", HKS Adjustable actuator adjusted to achieve 1.4 bar with no bleed off,"

i paid under 100$ for a hks EVC 4

The actuator is adjusted to give 1.4, what I mean is that the signal hose is connected directly from the comp cover to the actuator with nothing in-line. With this setup we still have the boost dropping.

Exhaust consists of a Long split front/dump, so long it joins at the cat, straight from japan, ultra-flow cat, and super dragger with resonator replaced for pipe.

Intake is a brand new PWR cooler, Apexi suction kit suit z32.

So i think all of that should be fine.

outta interest what rpm peak power at ?? mines higher than most ive seen obv due to cams and not alot of timing in there

6600 / 6700 peak for mine 264 in / ex hks cams

wot diff does 260 tomei's get ? gather quicker spooling as less duration?

From what I remember its around 6000, dont quote me though.

If you have adjustable cam gears then you should able to dial up the cams so as they bring the power on quicker, make the most of the cams you have.

Easy way to work out if it's the boost controller or not is to watch the wastegate flap on the dyno while the boost begins to drop.

If the flap is opening more as the boost drops then the wastegate or boost controller is the issue however if the flap stays constant or even begins to close then I'd say the compressor is simply out of flow.

6000+RPM on an RB20 with a GT2530 is getting very close to the end of the compressor map.

Easy way to work out if it's the boost controller or not is to watch the wastegate flap on the dyno while the boost begins to drop.

If the flap is opening more as the boost drops then the wastegate or boost controller is the issue however if the flap stays constant or even begins to close then I'd say the compressor is simply out of flow.

6000+RPM on an RB20 with a GT2530 is getting very close to the end of the compressor map.

Good advice. thanks.

Don't know much about GT2835's.

I'm gunna stick with this turbo coz it's great... providing I can get it to hold boost above 6500rpm

Engine is great. on 14psi for the last 3.5yrs that I've owned it and I've given it absolute curry every time I take it to the track. It loves it. 7900rpm all the time.

I've just bought a AVC-R and I think we're tuning tonight. We'll post up how it goes.

running 2835 would be like running a garrett 2871r - 3071r wouldnt it ? would make the power but larger exhaust housing would prob at the the rb20's classic lag problems ??

i run the above setup too ... car used basically track only... friggin good setup.. not too laggy except for small motokana tracks but anything else as said when on boost it holds right to limiter all day everyday and is very smooth

^^^^ let me know the results

I was going to tell you to go with a GIZZMO MS-IBC Russel but it seems it's to late now. I will have a look at my dyno graph from when I had my R32 tuned, was running HKS actuator with a AVCR but slightly different turbo, HKS2535 which is just a step up from what your running but same rear housing from memory so would be pretty close

From memory my turbo held power up to around 7200rpm but don't have the graph with me, will check when I get back. I remember putting a little extra per load on the actuator which helped boost controll but over all it wasn't the best

My AVCR spiked and ran like crap no matter how much we played with it

Cheers all for the help.

The AVC-R is a good unit, we were able to obtain a dead flat horizontal boost pressure with one of these boost controllers on a 3071R equipped SR (pretty hard hitting turbo), so hopefully, we can achieve the same on the RB20 with a good combo of preload and AVC-R settings.

Will let you all know how we go with it.

Grab a 2530 and look in the exhaust housing. The volute of the housing is tiny, Now put your hand over the exhaust at 6,000rpm and feel the air coming out. When you get so much back pressure in the exhaust housing perhaps its limiting the engines ability to hold boost at high rpm/cfm ?!?!?!??!

I dont know what that all means but a consideration

The HKS GT2530 is nearly identical to the Garrett GT2860RS.

Calculating the airflow of an RB20 at 1.4bar (assmuming 90% VE @ redline) results in approximately 43lb/min.

If you have a look at the compressor map of the GT2860RS you will see that 42lb/min at a pressure ratio of 2.4 is outside the compressor's rated operating region:

gt2860RS_739548_comp_e.gif

If you recalculate the airflow assuming boost of only 1.1bar, then at 8000rpm the engine is demanding 37lb/min of air. This is right on the max end of the compressor's map.

I'd say this is the problem man. The compressor is simply too small, and the boost is bleeding back to the region where the compressor is efficient at that rpm; 1.1bar.

Edited by Equinox

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 know why it happened and I’m embarrassed to say but I was testing the polarity of one of the led bulb to see which side was positive with a 12v battery and that’s when it decided to fry hoping I didn’t damage anything else
    • 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.
×
×
  • Create New...