AaronJ

iTrader: (4)

Hey guys. Recently I started noticing that my car no longer has a boost spike when I go full throttle (either by rolling into it or when shifting from the previous gear). It seems to hit 16 to 18 psi around 3k rpm where I used to get the boost spike and then slowly climb to 21 to 22 psi around 5k rpm. The only air handling mods I have is a K&N intake. The charge piping and intercooler are stock, and my front lip is immaculate so I know I've never bottomed it out. I have video of my boost guage from last fall (October-ish, when it started getting cold out) showing that it spiked to 25 psi. The only reason I took the video was because I couldn't believe that GMS1 could spike to 25 psi. It just feels like the torque doesn't come on as hard or fast as it used to. I still spin the stock conti's in 2nd but only when I get high up in the rpms. People still get boost spikes on GMS1 with the K&N right? My ltfts are only +6 to +8% so nothing really bad but I didn't know if there was a point where the car starts pulling power because its concerned about something.

Any ideas? So far I'm thinking the possibilities are: boost leak (idk how, everything is stock), one of the gms1 sensors loosened up and is leaking, or an abnormality with the tune (K&N bumps my ltfts to +6 to +8% according to my dashhawk). Thanks for your help.

1SLOLT1

My understanding the ecm controls boost based of current outside weather conditions and what elevation you are at. I've had different readings as you have.......I noticed different readings at night than the day time hotter weather.

AaronJ

iTrader: (4)

I know what you're saying, but I thought that was only when you were stock. Then the car would boost what it needed to make 260 hp so warmer/higher elevation it would boost more and vice versa. With GMS1 its just supposed to boost its maximum w/o overspooling the turbo, so colder/lower altitude would boost more because the air is already more dense coming in so the turbo pumps more lbs/min with the same amount of effort. Its probably around the same temp here now as when it was back in October. Also, its not the sustained boost I'm concerned about because it still hits 21 to 22 psi high up in the rpms, but its the lack of boost down low.

AaronJ

iTrader: (4)

Bump.

indy81

IDK...I know that when I first dynod with the GMS1 it went up over 25psi and was still going and I freaked out and let off because I didnt think it was supposed to get that high on a GM tune. I havent seen it do that since, usually it peaks at around 20 and holds around 17ish. If the car seems to be making the same power then I wouldnt think it should be an issue.

AaronJ

iTrader: (4)

Yeah it definately feels slower. I can't do a wheel spin comparison because I'm running pf01's with NT05's on them so they grip a lot better than the contis, but I took my srt4 owning roommate for a ride yesterday. The first thing he asked was whether or not I was actually giving her all she's got. Unfortunately I was. Tonight I think I'm going to use my dashhawk to clear out the fuel trims and what not to see if that is indeed playing a role. Otherwise I've got a set of injen charge piping that I was waiting to put on until I had a chance to order some longer couplers and t-clamps, but now I might just overnight some t-clamps (if I can't find any at fleet farm or something) and install that this weekend. If I do that I will try the soapy water test on the intercooler. I ran a rabbit over early last summer and it was tall enough that it knicked my front lip so I'm wondering if it hit the intercooler and stress cracked it. Then the cold winter made it brittle and the plastic actually cracked this spring. I guess I've got a lot to check. The last thing I wanted to do was replace the intercooler because I don't want to take off the front bumper.

In the end I'm just really trying to make sure that this thing is running perfectly fine before I hit Road America at the end of April. I'd hate to be running it on the track with a minor boost leak or something.

umrdyldo

iTrader: (1)

With GMS1, DP and intake you should be pushing up on 300whp.

My tires must be horrible because I can light them up in 1st and 2nd all day long.

Even a 40 roll in 2nd will spin for a quite a ways.

I only have GMS1

Wangspeed

iTrader: (2)

275-280 WHP on GMS1 is about right. There is no way you're hitting 300 unless you have an incorrectly calibrated dyno.

As far as boost goes, there's no guarantee on the amount of boost. It's targeting load numbers, not boost. I would also advise NOT putting the Injen pipe on with the stock IC. That is a combo that will likely cause your IC to crack. ZZP charge pipe, or leave it stock, or get an aftermarket IC.

AaronJ

iTrader: (4)

Well I'm running 235 wide NT05s now and I have yet to break them loose if I'm going straight. The stock conti's wouldn't make much noise in first, but in second once the turbo spooled you could hear them spinning.

I see. So then does it make sense that it ramps up as the rpm's climb? I would think that should be the other way around because the car would be creating a bigger vaccum force as the rpm's go up. I never heard that the injen would crack the stock intercooler. That's dissapointing because I was hoping to eliminate some head loss by swapping out that bendy straw we refer to as stock charge piping Even with some longer couplers, or the couplers with the bulge in them, so that they bend easier as the engine rotates?

Frogstofall

iTrader: (1)

You coming to the meet Saturday? We could check it out for you...

theamericanautos

iTrader: (1)

I have GMS1 w/ K&N SRI and the same thing happens with me. I believe it's because of the K&N intake. the stock intake is designed to create artificial boost in lower rpms (not 100% certain on that one but read it more than once). aftermarket intakes take away that effect. it should be okay

1SLOLT1

I do disagree with your statement sir!!

I hit 300 WHP and 335 WTQ with GMS1 and Catless DP on a DynoJet
I hit 266 WHP and 284 WTQ on a Mustang Dyno (GMS1 ONLY)

AaronJ

iTrader: (4)

Link? I know there is something goofy with our intakes because that's why GMPP never released an intake for us like they did for the sky and solstice.

Frogstofall

iTrader: (1)

No you didn't. Dyno sheet please.

SSlobalt

By Wanger"s account, the first dyno run you list would be an incorrectly calibrated dyno, and the second would be just about right for a Mustang dyno.

SSlobalt

Butt-dynos are notoriously inaccurate. You get used the higher power levels after a while. If you're not boosting as much as you used to, in the same weather conditioners, same altitude, and all that, then you can always do a boost leak test.

Wangspeed

iTrader: (2)

The Mustang dyno looks reasonable. The Dynojet one looks like, well, a Dynojet...

094doorSS/TC

Put your stock intake back on, see if there is a difference.

FRQ FLYR

iTrader: (1)

Possible bpv issue but you didn't mention cels or "limp mode" boost levels. If it were me and I couldn't find a boost leak I'd Seafoam that bitch-deposits build up worse in winter(so I've heard) and if you drive a lot in Wisconsin who knows.

indy81

I believe it is because of a MAF issue. When you add an aftermarket intake, some of the air being returned from the bpv escapes and is not cycled back through completely. It just throws the fuel trims off slightly between shifts.
Either way, peak hp/tq is higher with the SRI, I have dynod with my stock airbox and again with the intake and numbers were definitely higher with the intake.