Fuel smell after hard acceleration...

[sleepe]

1) When my Elise was NA I never got the fuel smell after a hard acceleration....now after a vf2 supercharger install, I smell fuel post hard acceleration. (my guess is the return-less fuel system spits out unused fuel out of the exhaust)

What is the cause?

2) I am also starting to get hesitation below 4100 rpms in lower gears.
(This is after allowing the engine oil to warm up according to the water temperature gauge at 189 F)
Does the oil in the SC itself need a warm-up period?

Robert

[cstetter]

Originally Posted by sleepe

1) When my Elise was NA I never got the fuel smell after a hard acceleration....now after a vf2 supercharger install, I smell fuel post hard acceleration. (my guess is the return-less fuel system spits out unused fuel out of the exhaust)

What is the cause?

2) I am also starting to get hesitation below 4100 rpms in lower gears.
(This is after allowing the engine oil to warm up according to the water temperature gauge at 189 F)
Does the oil in the SC itself need a warm-up period?

Robert

I have a FF275 and have the same smell after really hard acceleration. My wideband AFM shows ~10 sometimes since the tune is quite rich in order to keep combustion cooler and for less risk of detonation (I am no expert - just repeating what Casey at ForcedFed told me). I checked with them after I first noticed the smell and was told that the smell and AF ratio are normal for the kit and tune. In 5k miles and several track days, I have not noticed any ill effects yet.

I realize I don't have the same kit as you by any means but maybe this is useful information for you. Do you have a wideband AFM gauge in your car? It would be interesting to see what it shows during those hard accelerations.

On a side note, my car usually runs at a steady 186F and when I really get on it and run through a few gears at full acceleration, the coolant temperature can drop into the low 170s. Maybe you can observe the same? This was definitely not the case before the turbo conversion.

What is the cam switchover point with the VF2 install? Maybe you are feeling the hesitation of the cam switch?

Hope this helps!

[Kris from DRS]

Originally Posted by sleepe

1) When my Elise was NA I never got the fuel smell after a hard acceleration....now after a vf2 supercharger install, I smell fuel post hard acceleration. (my guess is the return-less fuel system spits out unused fuel out of the exhaust)

What is the cause?

2) I am also starting to get hesitation below 4100 rpms in lower gears.
(This is after allowing the engine oil to warm up according to the water temperature gauge at 189 F)
Does the oil in the SC itself need a warm-up period?

Robert

The return type, or returnless type, fuel system is not the issue. The map is probably slightly rich (which is OK), and the smell is probably unburnt fuel vaporizing off the catalyst or somewhere else in the exhuast.

Kris

[Kris from DRS]

also, try letting the engine decelerate for a period of a few seconds after hard acceleration (let it engine brake in gear). This might help reduce the smell you are describing.

kris

[sleepe]

Originally Posted by cstetter

I have a FF275 and have the same smell after really hard acceleration. My wideband AFM shows ~10 sometimes since the tune is quite rich in order to keep combustion cooler and for less risk of detonation (I am no expert - just repeating what Casey at ForcedFed told me). I checked with them after I first noticed the smell and was told that the smell and AF ratio are normal for the kit and tune. In 5k miles and several track days, I have not noticed any ill effects yet.

I realize I don't have the same kit as you by any means but maybe this is useful information for you. Do you have a wideband AFM gauge in your car? It would be interesting to see what it shows during those hard accelerations.

On a side note, my car usually runs at a steady 186F and when I really get on it and run through a few gears at full acceleration, the coolant temperature can drop into the low 170s. Maybe you can observe the same? This was definitely not the case before the turbo conversion.

What is the cam switchover point with the VF2 install? Maybe you are feeling the hesitation of the cam switch?

Hope this helps!

That's great insight. Thanks.

I think vision function uses a variable cam switch over, basically it enters high cam mod when you floor it. (but I am guessing on both counts)

The cam switch over might explain the hesitation, I'll have to ask vf.

Since my sc is intercooled, the faster I go the cooler it generally gets. But, it usually doesn't get below 185 at speed on a warm day.

When my Elise was NA: After the high lift cam engaged and I had thoroughly
rung out the engine, I would see coolant temperature drops as low as 170 sometimes. (from a starting temp of 190)

-Robert

[sleepe]

Originally Posted by Kris from DRS

The return type, or returnless type, fuel system is not the issue. The map is probably slightly rich (which is OK), and the smell is probably unburnt fuel vaporizing off the catalyst or somewhere else in the exhuast.

Kris

Thanks, I thought it was something to do with unused fuel.

Better rich than lean I guess

[Chococar]

If you replaced the fuel injectors, there's a possibility that they damaged the o-rings upon reinsertion. This happened on my car, which caused an air leak (but the closed loop control was able to compensate to a certain degree) and a fuel smell sometimes.