3071 surge

[QuattroFever]

mentioned in another thread my boost profile wrong so I started a seperate thread.

here are my boost curves.

boost01.JPG

boost02.JPG

here are my curves for boost control.

think I could be running lower in the rpm?

bear in mind with recommendations I am on a bone stock engine apart from ic, mani's, fuel sys. and zorst. stock rods no cr drop.

[A80Avant]

I see. I will look for my setup, although it was on 1.1.27 and had different boost settings. I believe that you can still run about 1.7-1.8 bar from 3600ish rpm with careful timing. If the stock rs2 turbo can do it, the 3071 can even though you are using stock parts. I have tried a safe setup on a friends rs2 which is also bone stock, only uses an 2.75inch exhaust

[Jamo]

Cripes that is a weird boost curve especially as you are requesting peak boost at redline

[QuattroFever]

can peak at 2bar then settle to 1.8. if I start going above 1.8 i'll have to put it in the midrange somewhere on spool. desperately need a better head.

drives nice though and is gentle on the engine and not an almighty kick up the a**e, just a firm squeeze up to speed.

[Jamo]

IMO the boost requests are far to low I'd want more boost in midrange and then trail boost to redline rather than at 5000-7200 redline requesting 1.8 bar boost

Who mapped it out of interest?

Why is it surging at so low boost?

[A80Avant]

These were my settings for the 3071 setup when i was using 1.1.27

setup included OEM rs2 IM, OEM rs2 EM, 3071R 0.63AR, scat rods, mahle pistons 440cc injectors, larger intercooler, standard wastegate with OEM spring slightly screwed in to hold boost higher on the rev range.

On 1.1.27, i dont think the DC curve made a significant difference, it was all about arranging the rpm vs boost curve in a way so that it doesnt spike. Even though i asked for 1.9bar till 7000rpm, i still got about 1.7 and i believe this was down to increased backpressure.







Looking at a couple of old logs, from target to actual(which is what you want, as target does not mean it will be reached), i had on 3d gear: 1.8bar @3560, 2bar@3700 and on 5th gear it had 1.9bar at 3300ish with fluctuations going between 280-286kpa. The only surge you could notice was the actual fluttering heard, but speedwise,or drivingwise, it was not passed through to you. On full onset of boost i had about 14deg timing on those runs.

A friends car at the moment has this curve and settings at 3/5 rather than 4/5 which allows more progressive N75 control. However although target boost is 1.8, it doesnt reach that, it only goes to 1.65ish and it all has to do with the boost settings on vems. On his car, controlling boost with the 4/5 boost control reference position created spikes on higher gears and was very difficult to control. His only difference from OEM is an intercooler which is OEM in size but aftermarket. His engine has done about 100K kms, and never been serviced. We tested this with an electronic version of detcans for knock and it ran nicely even with 95oct fuel. It did not surge by the way, and my car only surged on 5th slightly and 6th gear when i went WOT from 2500rpm and i was seeing 2bar at around 3200rpm. Sure, at that stage it would surge, but it was acceptable as it didnt last more than 300rpm on the range.

So for stock rods, you can be much more aggressive than you are on the boost, but just make sure when high boost is introduced it is either done gradually, or your timing is much lower than the knock threshold, as this will produce less torque, hence saving your rods.

I have only seen >60Nm of torque on the 3071R when pushed above 2bar and therefore you wouldn't stress your rods off limits if you hit 1.4ar at 3500 and 1.8bar at 3700. With a little less timing, it should become much more lively.

[prj]

Boost profile for 3071R with 0.82A/R at 100% throttle:



Boost profile for 3071R with 0.63A/R at 100% throttle:



Both cars on stock rods, 0.82A/R car has covered 2000 miles with very hard driving now.
Both cars on 1.8 bar springs IIRC.

I don't see how you guys are running 1.8+ bar to redline on 0.63 A/R housing. I get more power and better EGT's if I run ~1.7, because I can run much more timing.

Also, torque does not bend rods, knock does. No problem to ramp it up hard, or even getting one sparkle here or there (of course listen with your ears), but of course don't try stupid things 18 deg timing on peak torque on pump fuel, like many tunes are... /that/ will bend rods.

The magic surge point for me is the 3000 RPM mark on the 3071R turbo. If that is tuned correctly, everything else is fine, after 3500 RPM can treat it like normal.

[QuattroFever]

Who mapped it out of interest?

Me

[QuattroFever]

Looking at a couple of old logs, from target to actual(which is what you want, as target does not mean it will be reached), i had on 3d gear: 1.8bar @3560, 2bar@3700 and on 5th gear it had 1.9bar at 3300ish with fluctuations going between 280-286kpa. The only surge you could notice was the actual fluttering heard, but speedwise,or drivingwise, it was not passed through to you. On full onset of boost i had about 14deg timing on those runs.

yes, this is what I get. I can hear it chuffing away but doesnt affect performance in any way. I could just put up with it but I don't want to stress anything. doesn't sound good.

The DC curve is 1.1.81 is useful. I had problems with it underboosting and you just up the DC a little at a time until it meets target. If I had to pick the curve which best describes the power delivery it would be the DC curve.

I will experiment a little lower and see what happens.

[A80Avant]

With the curve that you have, it shouldnt make those sounds. I only had them as i mentioned above between 3200-3500rpm on 5th and 6th gear alone, and that was because i was getting very high boost early on. If you are getting those at 5000rpm then, there may be something else and not surge(unless the turbo is faulty). I never had surge on gears 2-4 on that setup. That chuffing away may well be the wastegate trying to keep 1bar at a range where the turbo is in it's highest efficiency and you are keeping it down. You are probably stressing the turbo more by asking 1.8bar to the redline

[prj]

Agreed. It is for sure not surge if it is over 4000rpm.

[Rusty]

Could it be the WG chattering due to the spring not being strong enough?

[QuattroFever]

its at 4krpm. Id get a video but u prob wont hear it over the exhaust.

Do you guys have ported heads? As i understand it you should typically see less pressure at redline if you have headwork or higher lift/duration cams.

Has anyone measured actual turbo rpm on a stock engine and seen final levels at optimum turbo rpm? Off subject a little but interesting

[Rusty]

The stock turbo on a 1.5 bar chip gives WG flutter between 3 and 4k RPM or so also, hence asking. If you're running a stock spring, then it might be worth taking advice on an upgraded one.

[QuattroFever]

The stock turbo on a 1.5 bar chip gives WG flutter between 3 and 4k RPM or so also, hence asking. If you're running a stock spring, then it might be worth taking advice on an upgraded one.

I had a high boost high timing chipset from mrc on an all stock setup bar the exhaust and never heard anything quite like this.

It makes sense though, id like to make it adjustable like i had on my old 3b. A stud in the WG cap to adjust the tension.