4.5 not liking under 2000rpm
Discussion
Just wondering if this is normal. I wouldn't say its hesitant or rough, but the engine doesn't like being under 2000 rpm will driving, it feels like it's just hunting for a little more go at a steady 2000rpm.
Starts and idles beautifully, accelerates like a cut cat, above 2000 rpm holding any rev its fine. Could this just be the map with the short induction installed?
I must admit it's taken me a while to adapt from the Chim 500 and have come to the conclusion; it only likes being driven in one mode, and that's fast. I'll save the city driving for the Chim.
Starts and idles beautifully, accelerates like a cut cat, above 2000 rpm holding any rev its fine. Could this just be the map with the short induction installed?
I must admit it's taken me a while to adapt from the Chim 500 and have come to the conclusion; it only likes being driven in one mode, and that's fast. I'll save the city driving for the Chim.
The AJP isn't a lazy engine like the rover v8. As standard it's not that happy below 2.5-3k revs as that's where all the torque comes in, 3k as standard. A good mapping sorts it out, or you just drive accordingly and don't try to pull from low revs. Mind you it revs to 8k...
Kits and Classics at Chesterfield is a great place for mapping, probably the recognised best for the MBE
Kits and Classics at Chesterfield is a great place for mapping, probably the recognised best for the MBE
I think it's a fairly common characteristic for the AJP8 to buck slightly at steady low tick over speeds. Mine has done this for most of the time I've owned it - never extreme, but you are aware of it.
It can been tuned out though if you persevere. I managed to get it running very smooth and steady this summer by replacing the throttle pots, changing the throttle link rod ball joints to rose joints (trying to remove as much 'noise' as possible from the throttles) and then recording a series of engine traces and dialing in the mixture settings. It now runs almost like a 'normal' engine at slow constant speeds.
At low engine speed with essentially no load, any changes in fueling reported by the O2 sensors or noisy throttle pots are immediately acted upon by the engine and hence the 'hunting' feeling.
Before second guessing anything though I'd record a series of traces and have a look at what's going on. Look for throttle pot spikes or imbalance between the banks. Check the adaptive values at the 2k range and see if both banks are similar, etc. If you don't feel comfortable with that, take it to a reputable tuner. They should be able to sort it out.
It can been tuned out though if you persevere. I managed to get it running very smooth and steady this summer by replacing the throttle pots, changing the throttle link rod ball joints to rose joints (trying to remove as much 'noise' as possible from the throttles) and then recording a series of engine traces and dialing in the mixture settings. It now runs almost like a 'normal' engine at slow constant speeds.
At low engine speed with essentially no load, any changes in fueling reported by the O2 sensors or noisy throttle pots are immediately acted upon by the engine and hence the 'hunting' feeling.
Before second guessing anything though I'd record a series of traces and have a look at what's going on. Look for throttle pot spikes or imbalance between the banks. Check the adaptive values at the 2k range and see if both banks are similar, etc. If you don't feel comfortable with that, take it to a reputable tuner. They should be able to sort it out.
Thanks for the replies, I think I'm over worrying it. "Bucking" seems an apt word. The annoying thing is, I have a comprehensive history folder from new, besides the obvious physical evidence of the short induction and finding posts from previous owners saying it was mapped too, there's nothing in the file. I'm pretty sure it was also de-catted in NZ, they arrived with the car in the boot, so that could perhaps be contributing to it being a little edgy under/at 2000rpm.
It's having preventive maintenance backlash buckets clearance check soon, so I will ask the engine builder who's looking after it to familiarise himself with the diagnostic software (I have purchased the cable).
The other thing I'll add, I try with city driving to keep a fairly low rpm, any time I back off at over 4000 it's like a fireworks factory explosion out the rear, and considering I used to give tosser's the bird when they gave it the crackle and pops outside my house, I kind of feel like a hypocrite!
It's having preventive maintenance backlash buckets clearance check soon, so I will ask the engine builder who's looking after it to familiarise himself with the diagnostic software (I have purchased the cable).
The other thing I'll add, I try with city driving to keep a fairly low rpm, any time I back off at over 4000 it's like a fireworks factory explosion out the rear, and considering I used to give tosser's the bird when they gave it the crackle and pops outside my house, I kind of feel like a hypocrite!
Edited by v8sag on Saturday 27th September 08:25
Decattng won't affect it. Mine is decatted, which is useful as it reducing the cabin temp and stops the gearbox/clutch/gearchange lever getting hot.
Bad news is the cats quieten the car by 8-10db at 4500-5000 revs.
I usually roll quietly/low revs out my close, even with a quiet exhaust system fitted.
Rolling back from 4000-3000 revs is right on form for pops and bangs on a mapped car
You might get flames
Bad news is the cats quieten the car by 8-10db at 4500-5000 revs.
I usually roll quietly/low revs out my close, even with a quiet exhaust system fitted.
Rolling back from 4000-3000 revs is right on form for pops and bangs on a mapped car
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