lift off crackle on overrun?

just been in my mates 52000 mile FRP mines done 89K and it just has this wicked lift off crackle/popping sound. At any rpm ya just lift off and it almost sounds like turbo lag crackle, but my FRP doesn't do it? should it?

I thought it maybe had an engine problem at first but it runs and pulls perfect.

We thinking it must be the exhaust system but its not a fancy magnex or Scorpion or original but a stainless system from the cat back, and another thing on bumpy roads when mine is fighting me his just stays true and straight mine is diving all over on the bumpy stuff is it the top mounts?

Can anyone shed any light

cheers

The overrun crackle/pop is one of the best things about the FRP, mines done it since day one and its mentioned in the early reviews of the car so I assume its a feature.

As regards the handling mine used to dart all over the road, solved it by fitting new lower ball joints.

But first thing I'd do is remove the wheels and have a good look around to see if there's something obvious like a bush knackered etc.

Yes it's supposed to do it, there are threads elsewhere which i can't recall where detailing someone else with it not happening.

[lisafrp]

There was one FRP that never used to do it, i cant remember the number, it was owned by Rob. It was looked into, but never solved, everything was as should be!

The popping/crackle on over run is essentially artificial, created by the mapping of the PCM. In the case of a normally aspirated carburated engine, with significant tuning, valve overlap & (preferably stainless) 4:1 or 4:2:1 branch exhaust header; Fuel supply is more akin to a controlled leak. On throttle shut off, fuel/air mixture is still admitted to the engine via the idle/slow running circuit. If exhaust temperatures at above the flash point of the fuel &/or the engine has significant valve overlap, popping will occur.
In injected turbocharged engines for example,this tendency can be exploited to reduce turbo lag, leading to a lick of flame & a fair bit of crackle, whilst the expanding gas produced kept the turbo spinning at a faster rate than it otherwise would have done.
In a modern day normally aspirated injected engine. on throttle shut off & whilst over running, ordinarily no fuel is used at all. In fact the same vehicle running down hill in neutral uses more fuel than one in gear.
Sadly this is very boring. The solution:- is to admit 3 or 4 spits of fuel as the engine over runs. Result:- snap, crackle & pop syndrome. Notice it only happens for a split second or so. To do so for longer would adversely affect fuel consumption.
Older carburated engines, like for like, will always use more petrol because the idle/slow running circuit is operational all the time the engine is turning. Consequently popping occurs all the way down the rev range on over run, provided there is sufficient heat &/or overlap to ignite the fuel. To my experience this is not the case with the FRP, which tends to do so as it passes through 4/5kRPM. I.e On changing up the box in the 6/7kRPM zone popping does not occur. It's on slowing/braking/passing lower RPM that popping occurs. This behavior, reminiscent of days & cars past, is part of the PCM map & sounds delicious, regardless of whether it serves any practical purpose or not.

#0083 was Rob's that did not over run, did 160 on the rollers from memory too

Also Sideleg runs these re poor driving experience:

or that fact i run comp TH2 wheels with spacers?

coopersmotors wrote:

The popping/crackle on over run is essentially artificial, created by the mapping of the PCM. In the case of a normally aspirated carburated engine, with significant tuning, valve overlap & (preferably stainless) 4:1 or 4:2:1 branch exhaust header; Fuel supply is more akin to a controlled leak. On throttle shut off, fuel/air mixture is still admitted to the engine via the idle/slow running circuit. If exhaust temperatures at above the flash point of the fuel &/or the engine has significant valve overlap, popping will occur.
In injected turbocharged engines for example,this tendency can be exploited to reduce turbo lag, leading to a lick of flame & a fair bit of crackle, whilst the expanding gas produced kept the turbo spinning at a faster rate than it otherwise would have done.
In a modern day normally aspirated injected engine. on throttle shut off & whilst over running, ordinarily no fuel is used at all. In fact the same vehicle running down hill in neutral uses more fuel than one in gear.
Sadly this is very boring. The solution:- is to admit 3 or 4 spits of fuel as the engine over runs. Result:- snap, crackle & pop syndrome. Notice it only happens for a split second or so. To do so for longer would adversely affect fuel consumption.
Older carburated engines, like for like, will always use more petrol because the idle/slow running circuit is operational all the time the engine is turning. Consequently popping occurs all the way down the rev range on over run, provided there is sufficient heat &/or overlap to ignite the fuel. To my experience this is not the case with the FRP, which tends to do so as it passes through 4/5kRPM. I.e On changing up the box in the 6/7kRPM zone popping does not occur. It's on slowing/braking/passing lower RPM that popping occurs. This behavior, reminiscent of days & cars past, is part of the PCM map & sounds delicious, regardless of whether it serves any practical purpose or not.

Cracking info....Cheers Dude...

My FRP 0117 doesn't crackle on the over-run either - it was just as quick as Dogsbody's - until he fitted his booster, that is.

Mike

MikeB wrote:

My FRP 0117 doesn't crackle on the over-run either - it was just as quick as Dogsbody's - until he fitted his booster, that is.

Mike

You will have to come out for a passenger ride with the nos on Mike. lots of fun. 200bhp makes the car come alive.

I will one day Graham, just not sure when I'll be back in the UK next.... Going to India to do a 950km Rally in an Auto-Rickshaw, just after Christmas-into the New Year. Wish me luck! I somehow think 7 hp will be very tame after 210 bhp in my ride over here in Korea!

Cheers,

Sounds very exciting