VZ CV8 and mods. What next?
Discussion
I've read quite a few comments regarding the tall nature of the gearbox fitted to U.K spec CV8s. Prior to the fitting of the full Wortec exhaust system including headers and a remap the car did feel quite lazy. Especially since fitting the headers the gearing feels alot more suited to the car in the sense that it just gets up to speed and through the rev range that much more quickly than when the car was totally standard.
I am now at the point where I am thinking about further mods. Do I change the diff or go for the supercharged option? Could it be that the longer legs of the CV8 spec gearbox might be more suited to bigger power?
Obviously supercharging is a lot more expensive than changing the diff and to be honest I am not all that bothered about out and out power for its own sake. More the ability to show a keen pair of heels to anything that I am reasonably likely to encounter on the road whether that be through better gearing or more power.
I am now at the point where I am thinking about further mods. Do I change the diff or go for the supercharged option? Could it be that the longer legs of the CV8 spec gearbox might be more suited to bigger power?
Obviously supercharging is a lot more expensive than changing the diff and to be honest I am not all that bothered about out and out power for its own sake. More the ability to show a keen pair of heels to anything that I am reasonably likely to encounter on the road whether that be through better gearing or more power.
Hello,
As Stig suggests I would really recommend the road response and Rip Shifter, both are excellent upgrades. Since having the 3.91 diff and Harrop cover the car feels much much quicker - however, I have to say I have lost about 2 MPGs on average, which is abit of a concern as now keeping revs as low as 1500rpm.
Cheers
Steven
As Stig suggests I would really recommend the road response and Rip Shifter, both are excellent upgrades. Since having the 3.91 diff and Harrop cover the car feels much much quicker - however, I have to say I have lost about 2 MPGs on average, which is abit of a concern as now keeping revs as low as 1500rpm.
Cheers
Steven
swordfishcoupe said:
Hello,
As Stig suggests I would really recommend the road response and Rip Shifter, both are excellent upgrades. Since having the 3.91 diff and Harrop cover the car feels much much quicker - however, I have to say I have lost about 2 MPGs on average, which is abit of a concern as now keeping revs as low as 1500rpm.
Cheers
Steven
As Stig suggests I would really recommend the road response and Rip Shifter, both are excellent upgrades. Since having the 3.91 diff and Harrop cover the car feels much much quicker - however, I have to say I have lost about 2 MPGs on average, which is abit of a concern as now keeping revs as low as 1500rpm.
Cheers
Steven
Steven,
So in 6th what MPH do you get per 1k Revs? - I know the standard on the CV8 is 42mph/1k RPM. 2 MPG is about a 10% loss on average, was thinking of getting mine done, but couldn't cope with those losses - (i do a LOT of miles)
wolfracer said:
swordfishcoupe said:
Hello,
As Stig suggests I would really recommend the road response and Rip Shifter, both are excellent upgrades. Since having the 3.91 diff and Harrop cover the car feels much much quicker - however, I have to say I have lost about 2 MPGs on average, which is abit of a concern as now keeping revs as low as 1500rpm.
Cheers
Steven
As Stig suggests I would really recommend the road response and Rip Shifter, both are excellent upgrades. Since having the 3.91 diff and Harrop cover the car feels much much quicker - however, I have to say I have lost about 2 MPGs on average, which is abit of a concern as now keeping revs as low as 1500rpm.
Cheers
Steven
Steven,
So in 6th what MPH do you get per 1k Revs? - I know the standard on the CV8 is 42mph/1k RPM. 2 MPG is about a 10% loss on average, was thinking of getting mine done, but couldn't cope with those losses - (i do a LOT of miles)
my 6.0 VXR does about 39-40mph per 1k in 6th i thought the CV8 had shorter gears than the VXR?
racebreed1 said:
wolfracer said:
swordfishcoupe said:
Hello,
As Stig suggests I would really recommend the road response and Rip Shifter, both are excellent upgrades. Since having the 3.91 diff and Harrop cover the car feels much much quicker - however, I have to say I have lost about 2 MPGs on average, which is abit of a concern as now keeping revs as low as 1500rpm.
Cheers
Steven
As Stig suggests I would really recommend the road response and Rip Shifter, both are excellent upgrades. Since having the 3.91 diff and Harrop cover the car feels much much quicker - however, I have to say I have lost about 2 MPGs on average, which is abit of a concern as now keeping revs as low as 1500rpm.
Cheers
Steven
Steven,
So in 6th what MPH do you get per 1k Revs? - I know the standard on the CV8 is 42mph/1k RPM. 2 MPG is about a 10% loss on average, was thinking of getting mine done, but couldn't cope with those losses - (i do a LOT of miles)
my 6.0 VXR does about 39-40mph per 1k in 6th i thought the CV8 had shorter gears than the VXR?
No, the CV8's are blessed (?) with the longest/tallest gears in the world. good if you're lazy, but it does get caught napping quite a bit if you forget to change down.
wolfracer said:
racebreed1 said:
wolfracer said:
swordfishcoupe said:
Hello,
As Stig suggests I would really recommend the road response and Rip Shifter, both are excellent upgrades. Since having the 3.91 diff and Harrop cover the car feels much much quicker - however, I have to say I have lost about 2 MPGs on average, which is abit of a concern as now keeping revs as low as 1500rpm.
Cheers
Steven
As Stig suggests I would really recommend the road response and Rip Shifter, both are excellent upgrades. Since having the 3.91 diff and Harrop cover the car feels much much quicker - however, I have to say I have lost about 2 MPGs on average, which is abit of a concern as now keeping revs as low as 1500rpm.
Cheers
Steven
Steven,
So in 6th what MPH do you get per 1k Revs? - I know the standard on the CV8 is 42mph/1k RPM. 2 MPG is about a 10% loss on average, was thinking of getting mine done, but couldn't cope with those losses - (i do a LOT of miles)
my 6.0 VXR does about 39-40mph per 1k in 6th i thought the CV8 had shorter gears than the VXR?
No, the CV8's are blessed (?) with the longest/tallest gears in the world. good if you're lazy, but it does get caught napping quite a bit if you forget to change down.
i presume the rest of the gears are much longer then as if 6th is only 2mph longer per RPM they are not that long?
By way of reference, a stock CV8 will be spinning about 1570 ish rpm at 70. With a 3.9 diff it will be circa 1900 which is about the same as a VXR8.
When i fitted one to the ute i didn't notice any real change in economy, but i dont realy do much motorway work at all. Clearly, if you do huge motorway miles then you will see a drop.
When i fitted one to the ute i didn't notice any real change in economy, but i dont realy do much motorway work at all. Clearly, if you do huge motorway miles then you will see a drop.
I haven't really seen a drop in economy changing from the MM6 to the M12 ratios. This is roughly equivalent to changing the diff from 3.46 to 3.9. I do do a lot of motorway miles to.
In my view it is a great improvement, and I guess it is to Monkfish's advantage that Vauxhall messed up and the UK VZ CV8s didn't get the M12 set from the factory as the Oz cars did.
In my view it is a great improvement, and I guess it is to Monkfish's advantage that Vauxhall messed up and the UK VZ CV8s didn't get the M12 set from the factory as the Oz cars did.
With your forum handle Mr Substiture, can I recommend an LSx of 454 cubes instead.
Here is a nice video on it for you to watch instead of East Enders http://gmtv.feedroom.com/?fr_story=e6eeea579c137d9...
Here is a nice video on it for you to watch instead of East Enders http://gmtv.feedroom.com/?fr_story=e6eeea579c137d9...
Edited by ringram on Monday 23 February 19:22
My very first post goes into more detail on the gearing:
www.hsv.org.uk/topic.asp?t=462202&f=69&h=27
My advice is to shorten the gearing unless you realistically intend to go for super charger or turbo conversion. Then the extra mid range urge should over come the tallness. If you stick with normally aspirated but make the lump more revvy then it will be even more important to get the gearing right.
www.hsv.org.uk/topic.asp?t=462202&f=69&h=27
My advice is to shorten the gearing unless you realistically intend to go for super charger or turbo conversion. Then the extra mid range urge should over come the tallness. If you stick with normally aspirated but make the lump more revvy then it will be even more important to get the gearing right.
Hi Wolfracer,
I will try and check the speeds per 1K later on in the week, TBH I do very little motorway driving and most of that is on busy motorways such as the M62 where you only get about 65MPH anyway.
The 3.91 has made the car a little noisier for me (all exhaust), it makes it a little more poppy etc but all within acceptable limits. The 2MPG is a worry though as you say 2MPG is pretty much 10% for me. Always got about 20-21 and with the cold weather I have seen a few 17.8-18 MPG !! Hopefully the new milder weather will help.
Cheers
Steven
I will try and check the speeds per 1K later on in the week, TBH I do very little motorway driving and most of that is on busy motorways such as the M62 where you only get about 65MPH anyway.
The 3.91 has made the car a little noisier for me (all exhaust), it makes it a little more poppy etc but all within acceptable limits. The 2MPG is a worry though as you say 2MPG is pretty much 10% for me. Always got about 20-21 and with the cold weather I have seen a few 17.8-18 MPG !! Hopefully the new milder weather will help.
Cheers
Steven
swordfishcoupe said:
Hi Wolfracer,
I will try and check the speeds per 1K later on in the week, TBH I do very little motorway driving and most of that is on busy motorways such as the M62 where you only get about 65MPH anyway.
The 3.91 has made the car a little noisier for me (all exhaust), it makes it a little more poppy etc but all within acceptable limits. The 2MPG is a worry though as you say 2MPG is pretty much 10% for me. Always got about 20-21 and with the cold weather I have seen a few 17.8-18 MPG !! Hopefully the new milder weather will help.
Cheers
Steven
Dude thats shocking. My 440 cube engine has averaged 22.9 MPG over 6000 miles, including many tailbacks on the M1 and 5 mile city commutes.I will try and check the speeds per 1K later on in the week, TBH I do very little motorway driving and most of that is on busy motorways such as the M62 where you only get about 65MPH anyway.
The 3.91 has made the car a little noisier for me (all exhaust), it makes it a little more poppy etc but all within acceptable limits. The 2MPG is a worry though as you say 2MPG is pretty much 10% for me. Always got about 20-21 and with the cold weather I have seen a few 17.8-18 MPG !! Hopefully the new milder weather will help.
Cheers
Steven
Yeah sounds suspect to me too 
But I cant be bothered finding some scientific data on the topic.
Volumetric efficiency is increased, but mechanical and thermal are reduced.
Maybe at a certain point in operation they will be better, but overall I doubt it. The efficiency chart should show where its best.
I know turbos are more efficient as their mechanical load is near zero other than an exhaust restriction, which can be designed around by proper exhaust and cam selection. So for them its just the thermal issue.. which can be partly addressed by proper intercooling.
It depends also by what definition. If you look at break specific fuel consumption then clearly that statement is totally incorrect.
(ie) Fuel required to generate power. NA is almost 25% more efficient on that basis.
But I cant be bothered finding some scientific data on the topic.Volumetric efficiency is increased, but mechanical and thermal are reduced.
Maybe at a certain point in operation they will be better, but overall I doubt it. The efficiency chart should show where its best.
I know turbos are more efficient as their mechanical load is near zero other than an exhaust restriction, which can be designed around by proper exhaust and cam selection. So for them its just the thermal issue.. which can be partly addressed by proper intercooling.
It depends also by what definition. If you look at break specific fuel consumption then clearly that statement is totally incorrect.
(ie) Fuel required to generate power. NA is almost 25% more efficient on that basis.
Gassing Station | HSV & Monaro | Top of Page | What's New | My Stuff