What should I expect and hesitation

[Race Grandpa I]

What should I expect and how many more runs should I make on the dyno

I have spent a lot of money tuning the engine with the previous tuner and 2 hours with the last tuner. I would like to limit the time on the dyno until I get acceptable results - not the best results. So here is where I am at. (Sorry no dyno charts to send to you.)

The last time time I had the car on the dyno it produced 145whp at 7,000 RPM on a Mustang Dyno with an AFR between 11 to 11.5. I am going back to see if I can get anything better with more time on the Dyno.

Even though the Tuner does not think I need a new ignition coil, I am going to have one installed. One thing that surprised me is that the Tuner only had two small portable fans instead of a large fan. The two fans blew air from underneath the car up at the radiator.

I am thinking that the Mustand Dyno reads about 15% below a DynoJet, which would make an upward adjustment of 15 to 20% or around 162whp. I do not know how to adjust for potential heat soak. We are at 200' above sea level. So maybe 15%. If that is correct, it would make an upward adjustment to 188whp.

However, that sounds a little high with an AFR of 11 to 11.5.

What do you think???




Problem with Hesitation.
Before I put it on the dyno the engine had a small hesitation between 3,000 to 4,000 RPM. One time I took a corner farily fast and for about 1 second it acted like it was out of gas. I have a JR fuel pump with 1,500 miles.

Any ideas what is going on and what needs to be done to correct the problem???

[Tom @ Fast Forward]

Paul,

I can't speak for the offset from DynoJet to Mustang or any other dyno. The raw numbers are not that important either. The key is the shape of the curve and the fuel curve. With these kits, the HP curve should basically be a straight line. If it drops off above 5000 RPM then we need to look at the fuel curve. If that is relatively flat (11 to 12.5) then we have to look at ignition. If fuel makes a turn at relatively the same place as the HP**, then fuel could be the problem. Without seeing the graphs, it is a hard call. Weak coils are common in Miatas. Especially when you boost them. The telltail sign is HP drawing a straight line to ~5500RPM and then rolling off with fuel staying steady.

Only worry about the real numbers rather than the curve when you are using a DynoJet. Don't take me wrong. I am not trying to say one dyno is better than another but DynoJets are consistent all over the world. Mark Dobeck did a good job when he did that design.

**Note that A/F from a tailpipe sniffer lags behind RPM as there is a time delay in the gas getting to the remote sensor. Depending on what gear you are in, you may see HP fall off at 5500 and fuel change at 6000, for example. They get closer in higher gears and farther apart in lower gears.

[Race Grandpa I]

Problem with Hesitation.
Before I put it on the dyno the engine had a small hesitation between 3,000 to 4,000 RPM. One time I took a corner farily fast and for about 1 second it acted like it was out of gas. I have a JR fuel pump with 1,500 miles.

Any ideas what is going on and what needs to be done to correct the problem???

[Tom @ Fast Forward]

No idea.

Did you have plenty of gas in the tank so it didn't move to one side of the tank and starve the pump?

Could you have a loose ign wire to the coils or a loose ground?

Is the bottom bolt (pivot bolt) of the alternator real tight? It is the ground return for power from the alternator and can cause all kinds of things under differing engine loads.

[Race Grandpa I]

No idea.

Did you have plenty of gas in the tank so it didn't move to one side of the tank and starve the pump?

Could you have a loose ign wire to the coils or a loose ground?

Is the bottom bolt (pivot bolt) of the alternator real tight? It is the ground return for power from the alternator and can cause all kinds of things under differing engine loads.

Gas tank was 1/2 full.

Will look at the next two on your list. :stuart:

Thanks,