Thinking of RC3, Scangauge enough to monitor boost?

Hi all,

I'm all stock, and thinking of going straight to RC3 with no other mods (18-18.5 psi boost). I know I would need to monitor boost since that is at the upper limit of the stock turbo. I have VCDS and Scangauge. I know that a mechanical boost gauge is the best, but would Scangauge be sufficient, especially with some VCDS logs occasionally?

I have no history of overboost issues, freshly cleaned intake installed, etc.

I generally don't have an opportunity to drive that hard (living in LA, have a baby, etc.), and I don't plan on using all the power all the time because I also don't want to blow my clutch too soon. Basically, interested in having the power when I want it, and as a first step to future upgrades as time, $$, etc. allow.

Bump.

Also, follow-up question, how likely is it to get overboost with just a tune and no other mods? I know people say that that stock VNT has tendencies, but I'm not sure I understand what that means or whether it is due to other issues with the car.

rc3 on stock nozzles? not sure what the point of that would be. Or in fact if it is even possible.

I've talked with Jeff and that is fine (max on stock turbo). IBW (indigobluewagon) also highly recommends it and ran a car for 20k that way (all stock +RC3).

It is a nice bump with stock nozzles, and I don't feel like I need new nozzles yet.

I just installed a Rocketchip tuned AHF110 ECU this weekend switchable between Stage 2 & 3.

Right now I am driving it on stage 3 and its a decent bump powerwise. I am also concerned but not really that worried. That being said I plan to install a boost gauge sooner than later and possibly just switch back to stage 2.

The stock map sensor can measure 2.5bar so I see no reason why your scan gauge is not good enough, but how easily can you read a little digital read out when you have your foot in it when it will be likely to over boost vs a gauge ?

alhdude said:

I just installed a Rocketchip tuned AHF110 ECU this weekend switchable between Stage 2 & 3.

Right now I am driving it on stage 3 and its a decent bump powerwise. I am also concerned but not really that worried. That being said I plan to install a boost gauge sooner than later and possibly just switch back to stage 2.

The stock map sensor can measure 2.5bar so I see no reason why your scan gauge is not good enough, but how easily can you read a little digital read out when you have your foot in it when it will be likely to over boost vs a gauge ?

Click to expand...

Yes, the refresh rate on the SGII and the ability to read it won't be as easy as a proper boost gauge, but I can also run a VCDS log and get good hard data, so that was my plan.

Sweet that you got an ASV tuned ECU. That is what I wanted to do originally, but not sure I want to spend money on an extra ECU plus a tune (CA emissions readiness test means that an AHF110 ECU wouldn't pass).

Have you hooked up VCDS to see how much spike or overboost you are getting now?

I have not hooked up VCDS as of yet to do any boost logs or anything else, will do sometime but I am not terrible hurry really. I am pretty gentle with how I roll on and off throttle but not afraid to floor it. Last time I checked my lower intercooler tank it had no oil puddling in it and never has so my turbo is decent in that respect.

I bought this tuned ecu used so I actually still have my original ALH90 ecu. Where I live on Ontario Canada has emissions readiness testing as well, I feel your pain.

When I do check boost I will post to this thread. Do you plan to do nozzles as well?

I'll do nozzles in the future when these wear out. I'm pretty sure these are still in pretty good shape (at least I have no reason to suspect them, and they show very well balanced in VCDS).

Where did you find the tuned ECU? That's a great find. Definitely update when you run some logs. I'd love to see.

I bought it from a fellow member here on TDICLUB in the Ontario subforum for $250 and we swapped it at his place this past sunday.

I just had put in a new MAF as my old one was only going to 450mg measured, and that alone was a bit of a bump in power.

My car has 475km which is darn close to 300k mi. I am still able to pull down more than 500km to half a tank (filling the tank till i don't hear air venting) I have not been able to do any straight highway runs yet with the new maf and tune, should be interesting.

If you look at another thread I started (when do you need a PD150 manifold) you will see some posts about VNT15's and boost spikes. Probably with a bigger down pipe we would be completely safe. My car shows no signs of clutch slip either but I have no idea if it has been done before (I bought it at 420km) the power also seems to "come on" right at 2000rpm as well below that it feels stock.

RC3 with stock turbo is a nice tune with great driving features. I liked it better than RC2. Then about 3 years later my turbo shaft broke and that is why I have RC4 now.

A analog boost gauge is in many respects superior to digital in that you do not have to read the number to see what is going on. I have a 40 psi analog gauge now and I know the boost when I am flooring it should be about 2:00 on the gauge, and my EGT should not be more than 3:00 (1200 degrees F). A quick glance is all it takes and when you are doing 115-130 mph that is all the time you want to spend.

Thanks, Chris. Good points (though I don't think I've ever gone over 100 in my car, not many opportunities to do that where I live). Yes, digital is not ideal for sure, but one expense at a time. I think a few WOT runs with VCDS logs would show me any boost issues.

When you were running RC3 on your stock turbo, did you have upgraded nozzles or were they stock also? Did you find that you needed to have a boost valve installed also with your setup? I'm leaning toward getting an RC2/3 switchable tune so that if I do encounter boost issues, I can dial the tune back until installing a boost valve or adjusting the actuator.

The difference between the ScanGauge and a real physical gauge with a needle sweep, which can be digital btw, is that the SG is pulling this info from your ECU so it's limited in update speed and latency. If you have a particular type of tune, you'll also have to deal with the diagnostic limit and converting that yourself. A physical gauge will be responding immediately and is one that is independent of the control system of the car, thus can be more accurate and/or precise.

DC. That's very helpful. I guess for my purposes I just want to do an initial check after tuning to make sure things are alright and set up. I was planning on doing that with VCDS and a few test runs. If necessary, I'll put in a boost valve. Alternatively, if I get a switchable RC2/3 tune, I'll put it on RC2 if I have overboost issues or spikes until I get things figured out.

Down the line, when I have more $$, and maybe want to mod more (nozzles or turbo, etc.), I can put in a proper boost gauge, but just hoping I can get away with SGII for the time being . . .

Does that sound like a reasonable course of action?

I have used a ScanguageII with Sprint 520 nozzles and a TDTuning stage 3 tune (see signature) for several years with zero issues. Like you, I don't go crazy and this is more than enough to monitor the boost and anything else. Now, when I up grade the turbo and push the boost to 26+lbs, I will want to install a boost gauge and a EGT gauge. But not till then. DC is running 200 horsepower and over 30 psi boost and has been for a couple of years now.

Thanks, John. That's very helpful.