got a slight problem with my FJ73 landcruiser, 4 ltr petrol/gas
i have cut most of the exhaust off the landcruiser including the muffler, the exhaust is now around 1 metre long from the firewall.
i have installed a lukey hot dog resinator to the end of the exhaust, hoping to re-gain the loss of back preassure without the muffler.
whilst this set up sounds great, nice and chunky. everytime i hit the go peddal i feel the cruiser struggling a little under power, compared to the old system that was removed.
it runs a little better on gas compared to petrol, but still sluggish.
how can i fix this problem? i still want it to sound great, still want it to have a short exhaust, car wont be used on the road so it does not have to be legal.
how can i restore the lost power of the old beast?
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exhaust power loss
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Re: exhaust power loss
Get it dyno tuned for the new exhaust.
Reduced backpressure (especially to the extent you have gone) is similar to a chunkier cam. I would guess it's now flowing significantly more air at low speed WOT, and isn't getting enough fuel i.e. it's leaning out too much when you hit the throttle. You probably need bigger accelerator jets on petrol, and NFI about the gas - I would say it would depend on the converter / system you use.
You may not be able to restore the very low-rpm (i.e. just off idle) torque you had with the restrictive exhaust - that's one of the trade-offs with engine design.
Reduced backpressure (especially to the extent you have gone) is similar to a chunkier cam. I would guess it's now flowing significantly more air at low speed WOT, and isn't getting enough fuel i.e. it's leaning out too much when you hit the throttle. You probably need bigger accelerator jets on petrol, and NFI about the gas - I would say it would depend on the converter / system you use.
You may not be able to restore the very low-rpm (i.e. just off idle) torque you had with the restrictive exhaust - that's one of the trade-offs with engine design.
Re: exhaust power loss
old rule of thumb
what ever you do to the exhaust do to the intake
ie:- free flow exh ...needs better air in to inlet( cold air)
what ever you do to the exhaust do to the intake
ie:- free flow exh ...needs better air in to inlet( cold air)
71 fj40 front shackle reversal +3" , 55 rear springs +3", 35 15.5 claws , 60 diff's 4wheel disc's , SOON TO BE WINDSOR V8 + 5 speed
74 fj40 stock but very clean
84 bj40 3b stock and unloved
74 fj40 stock but very clean
84 bj40 3b stock and unloved
Re: exhaust power loss
Get it on a dyno. As you releases the exhaust back pressure the efficiency of the engine changes and that requres jetting changes. Most exhaust shops make the same claim that if you go too big and loose back pressure that you will loose power and torque, the reality is if you vary the exhaust from standard too much then the tune is no longer correct and there is a power/torque loss.
Joel
Joel
-Pre trip inspections/ servicing
-Suspension/ custom modifications
-4wd Dyno & tuning
-Qualified mechanics
-Suspension/ custom modifications
-4wd Dyno & tuning
-Qualified mechanics
Re: exhaust power loss
thanks for all your help guys.
i will get it booked in verry soon.
cheers rob
i will get it booked in verry soon.
cheers rob
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