Went to the dyno today... scam?

[WillDuhhBeast]

So I went to the dyno today, a local ricer shop.


So they put my brothers supercharged celica up first. They get it to forth gear and as soon as they slam it.. a/f ratio goes sky high lean. So they mess around and see what the deal is a decide his tune is very bad (Note: he's been driving it.. and driving the HELL out of it for a month now since it was tuned/supercharged.) and they said he shouldnt even drive it to work.


So we are all shocked like damn, how could this be.


Next up was my car, and they put it up there.. slammed it.. and SAME thing. A/f ratio went sky high.. it looked like a vertical line straight up at 18. They said that my tune was also bad. I've had this car, on this very same tune for 8 months and at least 20+ track passes and numerous street encounters.


Did I get screwed? I dont see how my car could be so poorly tuned, for so long, and be driven like i drive it. I drive the HELL out of it.. I never hear knock. There is no bogging or hesitation. It accelerates smooth through every gear, all the way to the rev-limiter.


Did I get scammed?


My buddy that went before the celica's a/f was read normally.. so I'm left a little lost.

 

[crzyhrse99]

I'm guessing that you have a power adder w/ the numbers in ur sig, and since you have driven youre car for 8 months w/o a tune, I recommend that you should take ur arse to a reputable tuner and get a conservative tune before youre engine goes boom...just my .02

 

[thomas91169]

umm yeah, id suggest getting a secodn opinion by another shop that is very stang friendly and that can make adjustments to your tune to dyno it. 18:1 a/f ratio is very very very ****ing lean, most times for street cars on stock motors its kept around the 11-12:1 range for safety purposes, ive seen 13-14 on built motors that can handle the heat. 18:1 is just mind blowing if its true.

though id tell them to check their equipment as well, two cars that have been driven hard for long periods in a row, both show the same insane a/f consecutively? sounds like they need to possibly "clean their sniffer" so to speak.

 

[WillDuhhBeast]

The car was dyno tuned when the supercharger was installed. The runfiles from the original dyno show's a very safe a/f.




8 months later, they claim my a/f is off the charts. I hate the idea of having to pay more money for a second opinion. I know for a fact if my a/f was that out of wack.. i'd feel something, and it would have FOR SURE broken by now. There is no way my stock motor with 80k miles on it can handle consistant redline pulls in almost every gear, every weekend with 18+ a/f. The way the graph looked at the 18 mark was VERTICAL, which means it had no intention on stopping there.


I'm calling b/s on the dyno.. just hate to have to pay more money to prove them wrong.

 

[thomas91169]

a/f ratios change drastically under different atmospheric conditions, but not too drastic.

i had a 97 eclipse GST that i tuned via DSMlink, which allowed me to change every aspect of anything having to do with fuel, timing or airflow delivery, and was probably one of the best obdII loggers out there, 300 samples per second logging everything it could. What was tuned perfectly one day, would show knock the next (dsm's have knock sensors). i had the CEL rigged to blink rapidly if timing was retarded 3* due to knock, and i could tune and tune one night and have 0 knock and perfect timing, and be driving the next day with totally different conditions and boom, CEL starts going crazy, hook up the laptop and sure enough, getting knock cause the barometric pressure dropped, the temp outside was different, humidity, etc.

BUT i highly doubt anything regarding the weather would make the car run fine one day to super uber lean the next.

you could always get a wideband o2 kit and that way youll always have a real-time wideband gauge in the car at all times. 300$ insurance IMO, then again, what happens if that gauge shows 18:1 a/f tomorrow and then you have to spend another whatever amount of money on a new dynotune? then youre out even more what it wouldve taken just to throw the car on another dyno just for peace of mind?

IMO id just take it somewhere else, 50-70$ whatever for a few runs and peace of mind is alot better than however much it would cost to replace melted pistons and snapped rods. you gotta pay to play the game........

 

[katshot]

You can always install your own A/F gage.

 

[2000BLKGT]

Were they measuring the A/F from the tail-pipe or from a bung in the mid-pipe?....I'm guessing the tail-pipe?

the tail-pipe sniffers IMO, are not the accurate way to measure A/F.....and it's quite possible their equipment wasn't working properly

regardless (mid-pipe or tailpipe....flawed equipment or not)....pulling an 18 on an NA motor is a disaster in the making....pulling an 18 on a blown application....the thing should just plain grenade

if that was my car.....I'd be going to a Stang-friendly shop ASAFP......get her on the dyno.....and make sure she's alright.....and I'd be measuring A/F from the mid-pipe

 

[007]

Both cars being totally screwed in the same way seems unlikely. I bet they screwed something up with the test. You said it was a ricer shop right...

 

[DBMSTNG]

get a wideband 02. the Innovate LC-1 is less than $200. you can connect it to your Xcal2.

 

[WillDuhhBeast]

Thanks for the replies guys.

I'm going to try and get scheduled with a more reputable domestic shop soon. I know for a fact something wasn't right with thier machine.. but I'm still a little worried.

It was a tail pipe sniffer.. which I understand isn't extremely accurate. That still wont explain the off the chart a/f on two cars, back to back.

The guy who ran the dyno said if I get a second opinion and prove that everything is spot on, he will only then refund the money. I guess a ricer shop has to make its money some how?