Just purchased a supercharged S2K - stumbling issues

[kpflynn]

Hi all,

I just purchased a 2002 Vortech Supercharged S2000 last week, and had it shipped from it's home in Michigan to San Diego.

It has an older Vortech unit, a Comptech exhaust, and received a dyno tune while back East. Other than that it is stock.

I've been driving it all week and it's been absolutely perfect until tonight. It's quite a bit colder than usual for San Diego (44 degrees) and while sitting at a drive thru for 10 minutes the air fuel ratio meter suddenly plunged from it's normal 14.5 to 10.0, and the car begin to nearly stall. Leaving the drive thru, the car was hesitating on accelration, and would randomly begin to "buck" a bit while I very gently drove it home. The AFR was all over the place, from 10.0 to 16.0.

My main fear is that the car was tuned for 93 octane, and the 91 octane we use in California is messing with it somehow. Other than that, I'm at a complete loss for what could be wrong. I am, unfortunately, still trying to learn about these cars. I had the vehicle checked over at a shop before purchase who declared it was in great shape.

So my question to the community is twofold. First, what could be wrong with my car and what remedies should I try? Keep in mind I'm not mechanically adept which leads me to my next question. Where in San Diego can I take the vehicle or is there someone (who I would of course compensate) who can come to me to diagnose this?

Thanks so much!

[Chickwithastick]

Octane, and difference in altitude can make a HUGE difference.

[repiv]

Things to consider and look into:

1. Going from a higher altitude to sea level like you did should make the car run better when supercharged. I'm at 3500 feet and whenever I do a road trip to sea level, the car is so much stronger and runs so much better.
2. You say the car was "tuned". Does this mean the car has more than just the stock Vortech black boxes? If this is the case, then a re-tuned now would be in order. Typically with a stock Vortech set-up, there isn't much to tune. 2 points of octane drop from 93 to 91 should not do much either as the kit was designed to run on 91 anyway. Unless you had the ability to alter the timing severely to benefit from 93, nothing should have changed in the way the engine runs.
3. Check your sparkplugs. If you had other than OEM plugs, these may be acting up. In particular, copper racing plugs don't last long on a supercharged S2000 (about 5000 miles). Iridium plugs don't work well in a S/C'd S2000. It produces a miss. Bosche plugs don't work well in S2000s. The gap is very critical in a S/C'd S2000. It can't be too wide or the spark blows out at high rpm and this can cause fouling and/or plug tip disintegration. If the gap is too narrow, they can foul quite quickly.
4. Check your MAP sensor connection. Even though there is a MAP clamp on a Vortech, the connection still needs to be solid.
5. Check all the connections on the Vortech black boxes (if that's what you're still using). These should be all soldered. Crimped connections have been known to create problems somewhere down the road.
6. Clean your fuel injectors.
7. Check your fuel pressure and fuel pressure regulator hoses.

[Chris S]

How did they dyno tune the car w/ nothing but a Vortech S/C and an exhaust? Vortech uses a POS Split Second piggyback ECU which is non-adjustable.

I went through 4 or 5 of them, and returned my car to stock in frustration. At the beginning, it ran well on the gas, but could be kind of lurching in parking lots. Near the end, the electronics wouldn't allow VTEC to engage, and it was terrible all around.

Assuming you don't want to go back to stock, your best bet is to ditch the Vortech electronics and go w/ a custom-mapped standalone ECU.

[kpflynn]

Hi all,

Thanks for the suggestions! Most are beyond my level of competence but once I find a good shop I will be bringing these notes for them to check. I drove it earlier today and it drove flawlessly until I got home, where it promptly stalled out.

I definitely want to keep it SC'd. I will most likely eventually go with a standalone, but would prefer to avoid that expense right now if at all possible - wallet is still hurting from buying this car!

[repiv]

I will most likely eventually go with a standalone
So, how did you "tune" it before?

[kpflynn]

So, how did you "tune" it before?

I didn't. I just purchased this car 5 days ago, and in the stack of paperwork it came with was a dyno sheet and an invoice for "tuning". I have no idea what that entails as it simply has the stock Vortech units.

[repiv]

I didn't. I just purchased this car 5 days ago, and in the stack of paperwork it came with was a dyno sheet and an invoice for "tuning". I have no idea what that entails as it simply has the stock Vortech units.
OK, then I'd say it wasn't "tuned", just run of a dyno to see what the whp was. You can't tune a stock Vortech other than put in a different diaphram in the FMU. This isn't really tuning. It's just altering the fuel pressure to change the A/F to a more desirable range.
With this in mind, then you can't tune it now. Just check out the other points I talked about. I'll throw in another point ....................
8. Check for any vacuum leaks both in the Vortech kit and in the stock lines.

[kpflynn]

OK, then I'd say it wasn't "tuned", just run of a dyno to see what the whp was. You can't tune a stock Vortech other than put in a different diaphram in the FMU. This isn't really tuning. It's just altering the fuel pressure to change the A/F to a more desirable range.
With this in mind, then you can't tune it now. Just check out the other points I talked about. I'll throw in another point ....................
8. Check for any vacuum leaks both in the Vortech kit and in the stock lines.

Thanks for the clarification. I am definitely noting this all down and will hopefully find a good shop in San Diego in the next few days.

Even with this problem, this is the most enjoyable car I've owned in years!

[repiv]

If there's nobody in San Diego, I believe Vortech is in or near LA.

[Chris S]

If there's nobody in San Diego, I believe Vortech is in or near LA.

That wouldn't give me a great deal of comfort based on my experiences w/ them. They referred me to call Split Second b/c they couldn't help me.

[BMoreyS2K]

If you want to take your S2000 to a performance shop to get the most out of your car call my friends at Cavallo Motorsports 760-603-8321 in Carlsbad. Check out their site: http://www.cavallomotorsports.com

Cavallo does high end work on everything from Ferrari to custom hot rods. Otherwise I would give Pacific Honda or Hohen Honda a go. See you soon!

[Randy W]

Goon?