Outer Limits 4x4 Board

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?

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.

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)

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

thanks for all your help guys.
i will get it booked in verry soon.

cheers rob