Why does my GSX keep getting slower with each upgrade?

[volkerding95GSX]

Hey guys! I usually try and figure this stuff out by myself, but I have no idea what to do next and I am in way over my head. Any help would be GREATLY appriciated. So thanks in advance.

I am stuck in a rut with my DSM build and was hoping you could give me some advice and/or motivation to finish it. It's been disheartening because it seems like every "upgrade" I do to it makes it slower and run worse than before. This car is the first I've ever modified and I have next to no mechanical experience besides the few bolt-ons I've put on.

The eclipse felt the fastest when I first bought it. It pulled hard and never missed out. The only mods it had when I bought it was a small 16g, 1g BOV, K&N fpik air filter, HKS cat-back, Apexi electronic boot controller and a bigger fuel pump (unknown size). At this time everything was great and I had no CEL.

Fast forward after all the bolt ons I've added: (4" Forced Performance intake recirculated, Punishment racing SMIC hard pipes, Stainless steel tubular exhaust manifold, stainless steel 02 housing dumped to the atmosphere, Megan 3" downpipe and 3" Megan cat back with cat-delete.) Now it idles just a little rough, I have a CEL, and the car feel WAY slower than it used to. It doesn't pull hard under boost. The boost gauge reads 10 psi, however I feel nothing but a slow car.

I've done a boost leak test and there was a huge leak in the coupler right after the turbo amoung a few others, so I fixed all the leaks, but it only helped minimally. Still the same symptoms. The oil, spark plugs, and wires are brand new.

Where did I go wrong? Why is my car slower after I upgraded the bolt on parts? Is it a matter of installing too many breathing upgrades and no fuel upgrades? Or should my car still run strong with the upgrades I have?

I still have plans to buy bigger injectors, a wideband, and ECMLink, but that wont be for a long while, so I was wondering if there's anything I can do with my current set-up to make it run strong again. If not, I would love if you guys could give me a rule out check list or a list of parts I would need to get my car running right again. Let me know if you need any follow-up questions from me and I will do my best to answer. Thank you!

 

[awdjosh]

Instead of dishing out some Benjamins for a knock sensor you can try to put some plumbers teflon tape around the sensor threads and reinstall. I was getting phantom knock on one of my built motors and it cammed hard enough to shake everything and I guess it was just enough to throw the knock sensor off continuesly.

 

[LandSpeed-DSM]

In the event there is a black goo leaking out the back he will need a new one.

 

[H@xtGSX]

$52.49 for a knock sensor at Autozone here... I was just there a couple hours ago and asked for my own car. It's one of the few sensors I haven't replaced.

That does help. You idle doesn't sound that bad, honestly. Noisey lifters, a few clicks and ticks from the injectors, but nothing real obviously bad. It sounds like one of the pressure regulators is leaking. The pressure seems to build pretty quick though, so I can't say that is the cause with any certainty... It is possible though. Either that, or you may actually have a pre-turbo exhaust leak. Those tubular manifolds are prone to cracking at the welds, so look them over. Look around the head where the manifold gasket is at for any black soot. Make sure all the bolts are there and tight. Vacuum test the wastegate actuator. Check the wastegate linkage. Also, make sure there isn't a bung for an EGT probe that is missing a plug on the bottom side of the manifold. I have seen one placed like that before and the plug had rattled loose and fell out..... But..... That dump tube definently should not be open that soon.

The other thing to look at IMO is the 1g BOV on the uicp. It's likely to be around 20 years old, and they can fail in odd ways and cause some weird symptoms that, at least for me, didn't immediately make me think the BOV was bad. You should probably vacuum test it off of the intake so you can see when it cracks open or if it is sticking. Where is that vacuum line on it going? Isn't that supposed to be hooked up to the nipple on the top of the intake manifold after the throttle body? You may have some vacuum lines not hooked up right.

Looks like a nice 95. It's paint is still actually red and not fading pink... I.had to repaint mine. Pink doesn't suit me well. Someone took pride in that engine bay. It's nice and clean. It looks like you have most of the other stuff to make it run pretty fast already, and it looks like good quality parts too. Should be fun once it's running right.

 

[volkerding95GSX]

Where is that vacuum line on it going? Isn't that supposed to be hooked up to the nipple on the top of the intake manifold after the throttle body? You may have some vacuum lines not hooked up right.

Sorry about the picture quality, but I am pretty sure it is hooked up where you are saying it should be.

That does help. You idle doesn't sound that bad, honestly. Noisey lifters, a few clicks and ticks from the injectors, but nothing real obviously bad. It sounds like one of the pressure regulators is leaking. The pressure seems to build pretty quick though, so I can't say that is the cause with any certainty... It is possible though. Either that, or you may actually have a pre-turbo exhaust leak. Those tubular manifolds are prone to cracking at the welds, so look them over. Look around the head where the manifold gasket is at for any black soot. Make sure all the bolts are there and tight. Vacuum test the wastegate actuator. Check the wastegate linkage. Also, make sure there isn't a bung for an EGT probe that is missing a plug on the bottom side of the manifold. I have seen one placed like that before and the plug had rattled loose and fell out..... But..... That dump tube definently should not be open that soon.

That all sounds like good advice, and I'll def check those things out next time I look at it.

 

[H@xtGSX]

Ok, that's correct. In the video it looked like it was heading down toward the turbo, from what I could tell.

I think you have narrowed it down some. You know that dump sounds off, and we agree it shouldn't be open like that, especially not at so low of rpm. It being open would definently make the turbo spool like crap and feel weak. Each flow upgrade you have will increase exhaust pressure also... The wastegate is what adapts and controls that pressure through the turbo. That is where I would start looking.

I haven't ever had a stuffed up cat on a turbo before, as I normally remove them for flow. I think if there were enough back pressure though, it would force open the wastegate if it was severe enough. It's just hard for me to imagine that much back pressure, since the only time I have dealt with it was on naturally aspirated engines. I think it is feasible though... The dump tube would be the path of least resistance if it were really constricted.

(we're getting there, despite my stirring the pot earlier .... I think you are close to having this fixed)

...I spent about 2 weeks cleaning up the mess I was left with in the engine bay when I first bought my 95, and it still didn't look half that nice. It is almost there now, but my homeade uicp has jb weld on it and looks like crap still. Holds pressure, but not nearly as nice looking. I wish I could've found one in that condition. Most of the one I see here are thrashed. Polish that valve cover up smooth and it'll be a real eye catcher even to people who don't know jack about engines.

 

[volkerding95GSX]

I haven't ever had a stuffed up cat on a turbo before, as I normally remove them for flow. I think if there were enough back pressure though, it would force open the wastegate if it was severe enough. It's just hard for me to imagine that much back pressure, since the only time I have dealt with it was on naturally aspirated engines. I think it is feasible though... The dump tube would be the path of least resistance if it were really constricted.

I don't know if you're referring to my car about having a cat, but I have a cat-less 3" turboback. That's why my check engine light is on, it's not reading the rear 02 sensor that measures the cat. Anyways, thanks for the compliments on my car and the help on what to do to rule out the problem.

BEFORE I buy anything here's my plan of attack:
Do a proper boost leak test/ fix any leaks.
Borrow my friend's timing light and see what I find there.
Inspect to see if WG is opening properly with a hand/eye check.
Check for pre-turbo exhaust leak by: Inspecting my EM for any cracks or loose bolts, THEN turn my boost controller ALL the way up and see if I even can boost more than 10psi (carefully, of course). If I can't, then I probably have a pre-turbo exhaust leak and I will take my EM off and maybe even put my stock 2G back on.

Anybody else have additions I should add to my list before I buy anything? Also, I will be able to work on my car today or tomorrow, does anyone want me to take pictures or video of anything specific? THANKS!

 

[H@xtGSX]

I forgot that you didn't have a cat, even after having talked about that earlier.... Too much time past since we started this.

Using a timing light on your car will probably not tell you anything unless you have a 1g CAS on it. It'll look something like this if you do:

<img src="http://www.dsmtuners.com/gallery/files/1/3/0/6/8/7/imag0321.jpg" alt="Imag0321" />

95 CAS's aren't adjustable. The ECU handles the timing adjustments on 2g's with the stock ignition system. That is the 1g CAS I replaced my 95 CAS and CPS with. If you ever have a problem with the 95-96 CAS and have to replace it, you'll quickly see why the 1g swap is worth the extra fiddling you have to do.