ok what is more likely the cause of backfires in a race car?...

bad fuel mapping or a lopey race cam?

 

Could be partly because of the cam configuration, but it's more likely because they probably run rich maps in order to prevent detonation... as a result, some unburnt fuel will make it into the exhaust where it'll ignite from high temperatures. A TT Z32 will do it if you have downpipes + test pipes + blow off valves + rich map (such as a JWT ECU). My old Z used to do it frequently when I was WOT.

 

Fuel pressure, loss of spark, dead injector, debrie in the fuel lines can cause a missfire, mixture is too rich. I get a little popping during deceleration(off the gas), its been running a little rich. Could be a # of things...Race cars are set up different. Wheres this going? Do you have a specific situation?

 

I would have to agree with fuel here. My BUELL used to do it. Makuni carb and D&D race exhaust. Same with my 280. It is usally fuems igniteing in the exhaust, causeing it to pop.

 

ha ha, I need to read before I post. I will shut up now.

 

Overlap in cams lobes, and fuel mixture.
When you let off the gas all of the sudden, you can have plenty of fuel, and little air, and little compression. Making the fuel burn slow, and pop when the exhaust valve finally opens.
My Z does it some, and right now a lot, because of poor fuel atomization in my #1 weber thanks to melted venturis.

Not a problem on a track car. But, it's not desirable in a street car. I don't care myself.
My motorcycle does it really good when downshifting.

I no that if I coast in gear with the Z with the ignition off, then turn it on I can shoot a flame a few feet out of the tail pipe. Sounds like a shotgun going off. Keep tailgaters off the tail. haha

 

i get flamage on my car, but its from lack of smog equipment and sensors that probally needing to be changed causing a rich condition.

some race cars have a backfire system to keep the turbo spooled. its more a rally thing than any thing else though

 

and talk about some sick sounding cars! haha

 

I forgot all about that system... but yeah, more common on rally cars. Opens the exhaust valve early when the throttle is closed so that combustion will spool the turbo. Very bad for the turbos, though... not a system that'd be used on a car that wasn't being frequently rebuilt.

 

true dat ^^^^ but they have other anti-lag setups as well like the 2-step electronically controlled, though im sure not the healthiest also, its safer than the way rally cars do it by cause the explosions if you will to spool that bad boy up

 

your talking like Bee-R and the such?

 

heres the situation....

i watched this vid --> http://www.youtube.com/watch?v=G0L__fCUdmM

and left this comment quote:

"when did flaming exhausts become cool? that just means you got a bad air/fuel mixture or your plugs are skipping...

and if its one of those flame kits... LAME

look up bee-R thats real flames from real performance"

then i get this after i defend datsun engineering because some idiot thought he could trash imports, not knowing that everyone has access to his youtube acount and find that he worships VW's which to me is worse than rice imo

"you dont wanna rip on volkswagen. The number of Supercars on this planet that use Volkswagen engines is retarded and i find it embarassing to call a bentley continental, bugatti veyron, gallardo or spyker junk because theyre considered the best engineered supercars on the planet. Backfiring during startup has nothing to do with bad fuel mapping. I'm an automotive technology engineer and i reccomend you reading up. Backfire has to do with ignition timing, quality of fuel, cam overlap, fuel pressure, and the fact that racecars dont have catalysts. During startup, the engine is cold so fuel is going to want to puddle and condense on the cylinder walls and intake ports. It makes it into the exhaust and collects in the exhaust piping. When the engine heats up and starts making NOX gases (no EGR and nox is only formed over 2500 deg F) it oxidizes the fuel further but when it hits the air outside the exhaust, it flashes. Thats one emissions controlled source for backfire. The other one is just the cam duration. Lopey cam idles is caused by an overlap in intake and exhaust valves where they are both open at TDC between the exhaust and intake stroke. Variable cam timing is designed to reduce hydrocarbons making it into the exhaust (emissions control, not designed for performance). When the scavenging occurs (exhaust moves out and pulls air/fuel into cylinder) many times it will pull a large amount of air/fuel mixture into the exhaust. IT burns off. It has nothing to do with fuel mapping. 95% of the fuel injected into the cylinder is completely burned within 23 degrees of the power stroke. With racecars, your better off pumping in too much fuel than not enough.. Theres no EGR valve so you cant replace a lean mixture with exhaust gases as a filler so thats why it has nothing to do with "crappy fuel mapping". Engines measure incoming air by temperature and volume, they measure coolant temperature, exhaust 02 % and intake manifold pressure/vacuum so they arent gonna map anything wrong unless a sensor is junk. If you THINK you know what your talking about, dont post, if you KNOW what your talking about, feel free to correct someone."

He took all that time to type his flawed explanation of how fuel mapping cannot cause backfires, but it is true about the bentley continental, bugatti veyron, gallardo or spyker but VW will never put that kind of tech in one of their street cars...

 

Here's an idea... grow up and quit arguing on youtube.

And just because Bugatti and Lamborghini are owned by VW does NOT mean that they are the same. Different engineers, different technology. That's like equating a Cadillac to a Metro because they were both GM owned.

 

idk.... coulda swore cadillac and geo were both pretty shitty.... i wouldn't own either thats for sure.... well.... maybe a geo....

 

my aunt and uncle had a geo storm, it was an alright car

 

whats with you people and geos... dam

 

I would own this Caddy.

http://www.youtube.com/watch?v=uX9_Ux2oTXo

 

cheap, reliable, economical. whats not to like? i'd rather beat up a geo than my z for daily duty/bad weather. i've got my eye out for a tracker as a possible replacement the honduh.

 

whats not to like... muhaha... muHAHAha... HAHAHAHAH

 

hey like E said cheap economical and very inexpensive to maintain
and you can keep from racking up miles on you precious Z

 

LOL... I just realized you're 16 years old. Grow the hell up. Making fun of Volkswagens, arguing on youtube, now making fun of Geos... When I was 16, I didn't act like a little douchebag. Your parents should've bought you a Geo instead of that Z... then you might have some damn respect and you'd realize how retarded it is when other people talk sh*t just to sound cool.

VTB.

 

yeah dude he is like 16 he is a child. we are kinda learning to cope with it. sometimes he is alright. im just saying, its hard to not argue with some one being stupid, but how stupid are you to get into a youtube pissing match?

 

I seriously need to write the list out... I believe he just became something like the reason number 2,537,135,731 (give or take a few) that I don't want children...

 

that list will take a while. while i dont know if i want children, like, theres moments i imagine being fun, like teaching them about cars properly, or how dumb/funny they are from being clumsy when young, and then when they are older in high school and you can F with them like a buddy or something. that stuff will be fun. the rest though, yeah not so much.... oh and you can use them to do chores for you.

 

thats what nieces and nephews are for.