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vtluu
09-07-2005, 03:10 PM
A few weeks ago a Thunderhill I encountered some issues with "abnormal" boost pressure. Sometime during my second session I noticed that the car felt a bit anemic while accelerating; I took a few looks at my boost gauge and noticed the car was only boosting to 12 psi. I knew that could happen if the ECU detected too much knock (a bit odd since I was running about half-and-half pump and race gas at the time) so I figured, whatever, keep going and deal with it before next session.

Next lap around, much to my surprise I noticed that boost was up again. WAY UP. Going down the straight boost was holding steady at close to 24 psi all the way through redline. And that's pretty much the way it ran the rest of the day. I filled up with straight VP100 race gas, and saw boost holding at 24, sometimes close to 25 psi. The engine seemed to run perfectly fine, no audible misfiring or knocking, no stumbling at idle. The only related issue was that in the 6th session an upper IC hose joint blew and I had to limp back to the pits and repair it, but after I fixed that everything was good again.

A few observations:
- Engine setup is a WORKS turbo-back exhaust (DP + HFC + IP + ABM), WORKS P2R reflash (default 91-octane tune), JDM MR diverter valve, WORKS air filter.
- Temperature was warm but not hot, mid-70s before noon to low-80s in the afternoon.
- Boost profile was normal (peaking at 21, holding at 20 through redline) when doing freeway pulls the day before.
- I did a pull on the road leaving TH right afterwards--with a half-tank of VP100 remaining--and boost was more or less back down to normal again, peaking and holding around 21 psi.
- I've done a few pulls on the freeway since, and boost is normal.
- No check engine codes or anything the whole day (except for P0300 crusing along on the drive home; I get a P0300 code just about every other day).

If this behaviour (boosting high when running race gas) were by design I'd be thrilled, but Pete@WORKS was as surprised by it as I was. I took the car to WORKS and a cursory visual inspection didn't reveal anything abnormal. Wastegate actuator looked okay.

I'm going to borrow a pile of datalogging equipment to hook up to the car next time I'm at the track but in the meantime:
- What do you think might be the problem (and how can I find out)?
- Is there a problem? Or is the ECU somehow boosting higher in response to race gas (unheard of with the Evo, as far as I know)?
- What are the odds of my engine going kaboom at the next track event? :)
- What else can/should I do about it?

vtluu
09-07-2005, 06:54 PM
Don't everybody speak up at once or anything... :?

EvoVIII
09-07-2005, 07:36 PM
well done Tam, ur car is finally boosting up to 25PSI!! :lol:

ace33joe
09-07-2005, 07:43 PM
Is there any chance that your boost control solenoid and/or electrical connection were not stable at the track?

If the wastegate actuator vacuum connections are fine, I would suspect the boost control solenoid.

Just my guess though.

Cameron@xperformance
09-07-2005, 09:16 PM
hmmm i wonder if you were boosting 25 at any of the autoxs.......

vtluu
09-07-2005, 09:39 PM
If the wastegate actuator vacuum connections are fine, I would suspect the boost control solenoid.
That's possible I guess... Is there any way of checking other than swapping another unit in?


hmmm i wonder if you were boosting 25 at any of the autoxs.......
No, because I was on stock boost control back then. Don't you even try to insinuate that I wasn't SP-legal. :P

ace33joe
09-08-2005, 12:57 AM
If the wastegate actuator vacuum connections are fine, I would suspect the boost control solenoid.
That's possible I guess... Is there any way of checking other than swapping another unit in?

There is a way to check the solenoid at the service manual 15-5
(Basically, applying external voltage and vacuum (hand pump) to check whether it is opening right or not. Also checking resistance of the coil is on 15-6)

Hope this helps.

vtluu
09-08-2005, 02:22 AM
There is a way to check the solenoid at the service manual 15-5
(Basically, applying external voltage and vacuum (hand pump) to check whether it is opening right or not. Also checking resistance of the coil is on 15-6)

Hope this helps.
Thanks... it does... but it doesn't. :) I mean, I could check this when the car is cold, but what I should really do is check it when the car is manifesting the problem--i.e. between sessions at the racetrack when most of the engine bits are close to red-hot. I'd better wear gloves. :lol:

ace33joe
09-08-2005, 03:16 AM
Thanks... it does... but it doesn't. :) I mean, I could check this when the car is cold, but what I should really do is check it when the car is manifesting the problem--i.e. between sessions at the racetrack when most of the engine bits are close to red-hot. I'd better wear gloves. :lol:

Then you need to simulate that engine heat by testing the solenoid near an oven or a heater. Oh, how about a hair dryer, which also simulates the air flow in the engine room under racing condition? :) j/k

MitsuMan
09-08-2005, 06:40 PM
good idea (above) I only know that my Exede sometimes stays at like 12psi for some reason all I doo is turn the car off(coasting) and then restart while driving and it (reboots?) restarts and boost just fine I'm Gonna ask Shiv what he thinks but it doesn't really bother me

vtluu
09-09-2005, 06:41 PM
Did a few 3rd-gear pulls on the San Mateo Dyno... uh I mean Bridge... today. I was able to observe boost creep up suddenly to 24 psi very close to the limiter. I.e. the boost profile I saw was that it would hold boost at about 21 psi right up until I got close to 7500 rpm, whereupon it would shoot sharply upwards to 24 psi. I'm pretty sure that at the racetrack I was getting to 24 psi at a lot lower revs, but at least this is something I can look at.

lqdchkn
09-09-2005, 06:56 PM
Did a few 3rd-gear pulls on the San Mateo Dyno... uh I mean Bridge... today. I was able to observe boost creep up suddenly to 24 psi very close to the limiter. I.e. the boost profile I saw was that it would hold boost at about 21 psi right up until I got close to 7500 rpm, whereupon it would shoot sharply upwards to 24 psi. I'm pretty sure that at the racetrack I was getting to 24 psi at a lot lower revs, but at least this is something I can look at.

Tam, have you mentioned this to Pete yet?

Cameron@xperformance
09-09-2005, 08:38 PM
Did a few 3rd-gear pulls on the San Mateo Dyno... uh I mean Bridge... today. I was able to observe boost creep up suddenly to 24 psi very close to the limiter. I.e. the boost profile I saw was that it would hold boost at about 21 psi right up until I got close to 7500 rpm, whereupon it would shoot sharply upwards to 24 psi. I'm pretty sure that at the racetrack I was getting to 24 psi at a lot lower revs, but at least this is something I can look at.
so is the san mateo bridge your "racetrack" now :lol:

earlyapex
09-10-2005, 01:01 AM
the boost profile I saw was that it would hold boost at about 21 psi right up until I got close to 7500 rpm, whereupon it would shoot sharply upwards to 24 psi. I'm pretty sure that at the racetrack I was getting to 24 psi at a lot lower revs, but at least this is something I can look at.

sounds like something is wrong with your boost control big time. Since the works uses the factory control, I would check the line they modified and also the boost solenoid.

shooting up to 24psi at 7300+ rpms? That's safe! :P

vtluu
09-20-2005, 12:32 PM
Replaced the boost control solenoid last night. Tried a couple 3rd-gear pulls this morning and it doesn't seem to have changed--I still get a spike up to 24 psi just before bouncing off the limiter. I've heard Jamie says that's not unusual, so I don't know if the spike I'm seeing is related to the overboost I was seeing at the track.

earlyapex
09-20-2005, 12:33 PM
There is nothing usual about spiking to 24psi at close to redline.

Something is amiss in your system. Checked the wastegate? Checked the vacumn hose to the wastegate?

lqdchkn
12-03-2005, 07:34 PM
Bump, any resolution on this?

earlyapex
12-03-2005, 07:51 PM
Bump, any resolution on this?

yea, Tam is running 25psi till his engine melts. But he thinks its purty darn fast right now. :roll:

vtluu
12-03-2005, 11:30 PM
I run straight 100 at the track and detonation doesn't seem to be an issue; at the last track day, engine performance seemed to be fine... I need to go get the car dyno'ed sometime though. These days the turbo will basically boost consistently to 24-25 psi, unlike before where it only seemed to do it at the track. I don't drive the Evo much on the street anymore and when I do, I try not to go WOT for too long when I'm running on pump gas.

I'm starting to think it's worth running 25 psi just to piss Bryan off. :lol:

There doesn't seem to be anything wrong with the boost control system itself. I had an XEDE installed for a couple weeks and was able to create a boost control solenoid duty cycle map that lowered the boost level to a more reasonable 21 psi (or basically whatever I wanted). I think the WORKS P2R flash I have just needs to get its boost map scaled back a bit with my setup. It's possible that my setup--notably the intercooler piping--is causing boost to be higher than intended.

earlyapex
12-03-2005, 11:37 PM
I run straight 100 at the track and detonation doesn't seem to be an issue;

How do you know that? You can't tell when you are detonating.

vtluu
12-03-2005, 11:45 PM
I've had the ECU fall back to a low-boost map due to detonation before, and it's never done that. Yes there may be still detonation but if there is, it's not frequent. Keep in mind the P2 is tuned for 20-21 psi (sustained) on 91 gas. 3-4 more psi with straight race gas should be okay.

earlyapex
12-04-2005, 02:11 AM
Keep in mind the P2 is tuned for 20-21 psi (sustained) on 91 gas. 3-4 more psi with straight race gas should be okay.

Show me a chart where a P2 holds 21 psi. All the P2's I have seen have a snake for a boost curve.

vtluu
12-04-2005, 06:15 PM
Show me a chart where a P2 holds 21 psi. All the P2's I have seen have a snake for a boost curve.
http://www.worksevo.com/images/products/BoostGraph2.jpg
That's exactly how my P2 behaved when I first got it except I got about 1-2 psi boost thanks to the TBE.

earlyapex
12-04-2005, 06:46 PM
Show me a chart where a P2 holds 21 psi. All the P2's I have seen have a snake for a boost curve.
http://www.worksevo.com/images/products/BoostGraph2.jpg
That's exactly how my P2 behaved when I first got it except I got about 1-2 psi boost thanks to the TBE.

Show me a real-word chart where a P2 holds 21 psi, not a hand drawn fake graph from WORKS.

Here are some:

http://www.gruppe-s.com/DynoDay/MattH.jpg

http://www.gruppe-s.com/DynoDay/MarkW.jpg

http://www.gruppe-s.com/DynoDay/JohnM.jpg

http://www.gruppe-s.com/DynoDay/AliK.jpg

Sweet torque snakes!