We had our dyno day yesterday. Four blown Mustangs and 3 Ford GTs. Beautiful weather etc etc. On the way down I challenged a Mercedes CLK55 AMG and owned him. It was fun.

Upon arriving at the shop I drained my fuel and put in race gas (100 octane VP fuel). My car was second to go onto the dyno and right away there was a problem. The car was missing horribly. Very strange since it had never done it before. The car drove really good prior and it never missed. We checked all the normal things and finally decided on a new set of plugs. There's $100 spent. The day continued with a the GTs Making 754 HP, 734 HP and 650 HP. All nice cars.

An asian guy with a Whipplied GT Automatic was needing a tune badly. The tuner, Tony of HP tuning in Florida, took him from 350 rwhp and 310 or rwtq to 450 rwhp and 420 tq. This was done in three pulls. Needless to say they customer was extremely happy.

My turn came and we still had the miss as soon as boost came in. It was so strange. The tuner overcame it by putting a ton of timing into it and finally made 555rwtq and 535 rwhp @ 15.5 psi. Really nice flat curve, A/F at 11.8. I knew the car would need to be adjusted during the road test because turbo cars always make more power (load differently) on the street. Sure enough the car has some detonation so the tune was modified and the miss came back. We talked about it and decided I would need to do some more data logging and work by email since we were out of time.

Sactown got on the dyno with his larger heat exchanger, 3.4 pulley and maybe something else, I forget. His car missed and detonated so bad he couldn't even complete one dyno pull. We stopped work and all began to talk about it.

After talking, we finally realized we were the only guys who used the race fuel from a local pump in town. I used 5 gallons from another pump and 5 from the local pump, Sactown used 10 from the local pump.

I reloaded my daily driver tune which made 450 tq 430 hp (@8 psi, the car makes 10.5 on the street so 490tq and 470 hp is probably pretty accurate) and the car ran like crap with the race fuel in it. I drained as much as I could and then put 13 gallons of shell 91 in. Car ran better better but nowhere near 100%.

The good thing is I have a tuner who will actually return my phone calls or emails and we can send data logs back and forth to get things dialed in.

The bad thing was having crap gas in our cars.

Steve is going to talk to the station and see what they say. I doubt they will do anything.

 

Sorry about the crappy gas.... but you've got a nice setup going on...

 

I've seen something similar happen and it's a real PIA, a tank or two of gas later and some logging and you'll be good to go

On a side note, you said the load is different on the street for turbo car? Does a loaded dyno not solve this problem?

 

Refill your tank at another station and keep the bad gas for your lawn mower...
At least, the good part of the day was to teach that AMG who was boss

 

[QUOTE=EagleStroker;5919733]
On a side note, you said the load is different on the street for turbo car? Does a loaded dyno not solve this problem?[/QUOTE]


Yes, I'll try to give a short explanation. Someone else may chime and further expand.

Turbos work off of heat with a combination of airflow. Both of these things are created by combustion in the motor. Combustion in the motor is dependant on how much fuel and spark is in the tune. The heat from the combustion will vary based on the load placed on the car. The dyno can simulate resistance and put a load on the car. Every dyno does this. Dyno's measure acceleration over time. What a dyno cannot do is give a specific load onto a specific car (this is actually not 100% true because there are some dynos that have adjustments to get really close). It also cannot recreate wind drag, which in it's self is another load placed on the car.

So tuners who tune turbo cars will always get a really good tune on the dyno and then road test while data logging because the car will spool up quicker and usually make more boost if the system is set up that way.

 

And I had a witness/passenger in the car. He pulled next to me at about 70 and I dropped into 3rd. He looked at me and just nailed it pulling a couple cars. I passed him by then end of 3rd and was a few ahead in 4th.

Then he continued driving all fast and crazy in and out of traffic so I decided to let him keep going.

 

It really sucks for these gas stations to play the games they do. My brother filled up his car the other day and it took 24.2 gallons. Real funny to find out later that his car has a 22 gal gas tank. Cant do much really once ur gone.

 

Thanks for the input Simon. I am a firm believer that data logging is the only way to have a really solid tune, just curious. I know that there is a huge difference between my tuners Mustang Dyno and a Dyno jet in town, my car finished it's pull 5 seconds faster on the Dyno jet since theirs isn't a loaded one.

On any account sounds like a fun day, and pics of said race or it didn't happen

 

Its gonna take a while burn 18gals of 100 octane in my mower. I car is running fine on the 91octane, will be putting it on the dyno Tuesday hopefully to get the tune dailed in and she what she is making on the 3.4. Look for 460 to 470 on 91 octane.