V8 Vantage - Low engine braking?
Discussion
I have a 2007 V8 Vantage with a clutch pedal. One thing that bothers me about the car is a lack of engine braking. When I take my foot completely off the gas pedal, the car barely slows down at all. I'm trying to figure out why (and if it's all V8 Vantages, or just mine). I've only ever driven one other, and it was a brief test drive...I don't remember it doing this, but I was unfamiliar with the car, and I wasn't looking for this behavior specifically. It feels almost like letting off the gas in an automatic car—not quite, but almost.
My assumption is that a high-compression, high-revving NA engine would provide quite a bit of engine braking off-throttle, which is what I've been used to with older cars. Perhaps there's a computer involved that's keeping the throttle open a bit for some reason? Something something IAT?
I don't believe this would be described as rev-hang, because the engine revs go up and down swiftly in neutral and with the clutch in.
The air intake tubes are "custom", and I'm assuming the air filters are some manner of "high performance" cone, but I haven't opened the box up yet. I plan to restore the tubing and filters to stock, clean the throttle/MAF, and see if anything changes (I don't expect it to).
According to the previous owners of my car, it has a tune of some kind. It is entirely undocumented, so I don't know what that means in my case. I plan to have a stock tune put back on the car (which I assume is a reflash of some kind—if anyone can steer me towards info on this, I'd appreciate it), but not knowing what was done previously, and knowing that, like, engine braking doesn't exactly reduce horsepower, I dunno why anyone would intentionally do this. I would not describe the previous owners as knowledgeable enthusiasts.
Can anyone with a known-stock V8 Vantage care to chime in about the way their car behaves? I don't want to go to great lengths to increase engine braking if it's behaving as designed, but it would be nice to have more.
My assumption is that a high-compression, high-revving NA engine would provide quite a bit of engine braking off-throttle, which is what I've been used to with older cars. Perhaps there's a computer involved that's keeping the throttle open a bit for some reason? Something something IAT?
I don't believe this would be described as rev-hang, because the engine revs go up and down swiftly in neutral and with the clutch in.
The air intake tubes are "custom", and I'm assuming the air filters are some manner of "high performance" cone, but I haven't opened the box up yet. I plan to restore the tubing and filters to stock, clean the throttle/MAF, and see if anything changes (I don't expect it to).
According to the previous owners of my car, it has a tune of some kind. It is entirely undocumented, so I don't know what that means in my case. I plan to have a stock tune put back on the car (which I assume is a reflash of some kind—if anyone can steer me towards info on this, I'd appreciate it), but not knowing what was done previously, and knowing that, like, engine braking doesn't exactly reduce horsepower, I dunno why anyone would intentionally do this. I would not describe the previous owners as knowledgeable enthusiasts.
Can anyone with a known-stock V8 Vantage care to chime in about the way their car behaves? I don't want to go to great lengths to increase engine braking if it's behaving as designed, but it would be nice to have more.
In comparison to other cars/engines, I find that my 07 V8V has low engine braking capability as well.
I somewhat learned to live with it over time.
Similar to your assumptions, I think it may be programmed into the throttle valve characteristics - most likely as a safety precaution to avoid the rear tires locking up during hard downshifts.
Another thing I observed once on a vely long steep downhill stretch of road is that the momentary fuel consumption didnt decrease as steep as on other cars when rolling downhill with closed throttle. That points into the same direction (open throttle & fuel), however could just be different integration length in the calculator...
I was not able to find a answer yet, but I think driving would be a bit more precise with stronger engine braking as you could adapt finer corrections during cornering etc.
I somewhat learned to live with it over time.
Similar to your assumptions, I think it may be programmed into the throttle valve characteristics - most likely as a safety precaution to avoid the rear tires locking up during hard downshifts.
Another thing I observed once on a vely long steep downhill stretch of road is that the momentary fuel consumption didnt decrease as steep as on other cars when rolling downhill with closed throttle. That points into the same direction (open throttle & fuel), however could just be different integration length in the calculator...
I was not able to find a answer yet, but I think driving would be a bit more precise with stronger engine braking as you could adapt finer corrections during cornering etc.
Tremelune, I cant help you with the engine braking question other than to say with my 2009 4.3, I have not noticed any change to this since having it tuned when I had the twin plate clutch/flywheel fitted along with high flow CATS, new filters with airbox delete etc. and remap.
If you are wanting to put your car back to stock, I have two perfectly good airboxes that I'm happy to sell to you should you wish. They are in perfect working order and would save you a hefty price tag if looking to buy from AM themselves I'm sure.
Have you not got any idea as to who did the 'tune' on your car? as if you did it might be worth asking them to remap it back to stock as surely they would have kept the file.
Looked to see of you accepted emails but you dont so cant communicate with you privately.
If you are wanting to put your car back to stock, I have two perfectly good airboxes that I'm happy to sell to you should you wish. They are in perfect working order and would save you a hefty price tag if looking to buy from AM themselves I'm sure.
Have you not got any idea as to who did the 'tune' on your car? as if you did it might be worth asking them to remap it back to stock as surely they would have kept the file.
Looked to see of you accepted emails but you dont so cant communicate with you privately.
Edited by BiggaJ on Monday 10th May 15:17
scampbird said:
I thought the poor engine braking on the 4.3 was due to the use of a ship anchor as a flywheel. 4.7 got a slightly lighter one didn't it?
Thought along similar lines in the beginning - but I guess the acceleration between reving the engine and engine braking is a order of magnitude different.So in my view the resistance generated from sucking against a closed (?) throttle without fuel beiing fed is the main driver in engine braking, followed by frictional losses. I may be wrong, though.
On the other side I never read about increased engine braking in the dual-plate clutch upgrade threads.
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