gu 4.5 gurgle sound when on gas..!

Post by **simcoe** » Thu Oct 25, 2007 8:32 am

It been a long time writing this up but ever since i had the conversion done i have had a gurgle sound coming out the exhaust when on gas and coasting ie not touching the accelerator while going down a hill etc.
At first thought it was a hole in the exhaust but not so.. so took it back to the gas man, he plugged his computer in and had a fiddle.
Prob about 1 hours worth of tuning trying different stteings etc and he couldnt get rid of it! I have a 2.5inch exhaust with 2 mufflers so it beats me how gas is making its way out the back and igniting??!!
Apart from this minor prob my trucks been unreal with the gas installed.oh its an airrod system to.

any help would be great
cheers

Post by **waxhead..** » Thu Oct 25, 2007 9:41 am

Its thought that this is pretty common with vehicles running on gas, as I know of a few that do it myself, my brothers GQ 4.2 on gas for one.

Post by **simcoe** » Thu Oct 25, 2007 10:36 am

my old rb30 used to do it on gas but it also did it on petrol..had a fiddle with the fuel screw on the carby and it fixed it!
being all computerised i assume the 4.5 is different.??!!

Post by **WOZ** » Thu Oct 25, 2007 11:56 am

The 4.5 efi engine management system shuts down the injectors on over-run. The gas is still being drawn into the engine on over-run even though it is only the idle amount.

Post by **simcoe** » Thu Oct 25, 2007 7:12 pm

so is there a way to fix it?? or lessen the serverity of it??
or is it one of those patrol symptoms

cheers

Post by **blownba** » Thu Oct 25, 2007 7:48 pm

WOZ wrote:The 4.5 efi engine management system shuts down the injectors on over-run. The gas is still being drawn into the engine on over-run even though it is only the idle amount.

You got it in one.
It depends what system you have installed, my guess is that its a Impco system, in this case de-accel fuel cut off is very hard to achieve.
If you had a injected LPG system you wouldn't see it.
Funny though my mates 4.5 with Impco doesn't do it with the standard exhaust.

Are you sure your cat is not hollowed out????

Post by **MyGQ** » Thu Oct 25, 2007 9:37 pm

Well my old GQ used to have this on gas and petrol to a lesser extent on my 4.2L Dual Fuel, but i was also running Extractors and 2.5" system. if i decelerated between 2000RPM and idle it would gurgle, above 2000RPM and decelerating it would be smooth drone, but dropping to 2000RPM or below made it sound like it had bubbles in the exhaust,

Never worried me, cause it sounded nice as far as i was concerned.

Post by **simcoe** » Sat Oct 27, 2007 7:35 am

Are you sure your cat is not hollowed out????[/quote]

what cat??!!

i did gut it out but then the exhaust made a ugly zing noise while under load..so got a hotdog put in place! All good again!
think i should put a nissan cat back it the spot???

and it's an Airrod system

Post by **love ke70** » Sat Oct 27, 2007 3:10 pm

if you run it on gas all the time you dont need a cat, but if your running on petrol i would put a hiflow cat of some sort in there, big fines from the EPA if your caught not running one.
as people have said, the noise is because you are getting the idle amount of fuel being drawn through, and thats more than what is getting burnt under decel, and with the larger exhaust, you can note the noise. i wouldnt worry about it if i were you...

Post by **blownba** » Sat Oct 27, 2007 7:38 pm

You are gonna need a cat fitted to be legal or roadworthy. And as stated the penalties from the EPA for not having one are pretty extreme to say the least.

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gu 4.5 gurgle sound when on gas..!

gu 4.5 gurgle sound when on gas..!

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