65mm throttle body on vr v6 recommendations.

[Frandy]

so 68mm is the limit....how big is it stock?? Isn't it about 65mm?? Is it worth the extra 3mm if you only have a full exhaust incl. extractors & hi flo cat and an airfilter??

 

[silvr6]

68mm is how big the elbox is anything bigger your wasting your money

 

[vr5speed]

i am doin the 65mm upgrade on mine this week i have cai,exhaust,power gold chip,k&n i notice a big difference when i put the chip in had better throttle reponse but will get better with the 65mm i was told so ill give it a try y not

 

[Immortality]

you can fit a 70mm, clean out the elbow with a die grinder to make it the same at the TB. the elbow opens up quickly from the TB s there is no restriction there. standard size TB on VN - VR V6 is 60mm(buick) ecotec V6 is 64mm. VN up 304 V8 is 65mm standard which will bolt straight onto the buick V6. also, as per greenfoams excellent thread, check that the butterfly is fully open when the cam is againt the throttle stop as most tend not to be, the fix is a simple one, grind the throttle stop until the butterfly is fully open. the only real advantage ofthe bigger TB seems to be that you require less throttle % for the same air flow hence you seem to be using less go pedal then before. the biggest restriction in an engine will always be the valves. so fitting high ratio roller rockers from YT in conjuction with a larger TB is probably the best way to go

 

[Cheap6]

Given that the Formula Holden engines make 280-300BHP using the standard V6 t'body and inlet manifold (matched to ported heads), I also question the value of swapping on a larger t'body at all. There may be a small reduction in friction due to the increased area, provided that new airflow losses aren't generated by introducing a step in the intake path. That would be covered by the posts about matching the manifold to the t'body.

Having said that, the rules for sizing a t'body on EFI engines are different to those for carbs, where a venturi vacuum is required for fuel metering. Beyond driveability issues, readily addressed with pedal/cam geometry, I can't see that it is possible to go too big with a t'body on an engine with EFI, solely looking at power output.

The downside of fitting a larger t'body to an auto trans car, as has been mentioned in another thread, is that the auto. shift control relies on throttle position as one of the inputs. Changing the relationship between the throttle angle and airflow screws with the gear changes.

 

[Immortality]

Given that the Formula Holden engines make 280-300BHP using the standard V6 t'body and inlet manifold (matched to ported heads), I also question the value of swapping on a larger t'body at all. There may be a small reduction in friction due to the increased area, provided that new airflow losses aren't generated by introducing a step in the intake path. That would be covered by the posts about matching the manifold to the t'body.

Having said that, the rules for sizing a t'body on EFI engines are different to those for carbs, where a venturi vacuum is required for fuel metering. Beyond driveability issues, readily addressed with pedal/cam geometry, I can't see that it is possible to go too big with a t'body on an engine with EFI, solely looking at power output.

The downside of fitting a larger t'body to an auto trans car, as has been mentioned in another thread, is that the auto. shift control relies on throttle position as one of the inputs. Changing the relationship between the throttle angle and airflow screws with the gear changes.

so what is the formula specs on the engine to make 280 - 300hp? the bigger TB probably has greater benefits on much more developed engines but doing it now certainly shouldn't hurt performance i don't think it's going to make a difference with the auto unless you have a 4L60E tranny which is electronically controlled. the older T700 hydromatic box uses a kickdown cable so should still behave the same.

 

[Cheap6]

so what is the formula specs on the engine to make 280 - 300hp?

Briefly, cam, roller rockers, ported heads, bigger valves, 10:1 compression.

the bigger TB probably has greater benefits on much more developed engines but doing it now certainly shouldn't hurt performance

No, but it's probably not worth spending the money either.

i don't think it's going to make a difference with the auto unless you have a 4L60E tranny which is electronically controlled. the older T700 hydromatic box uses a kickdown cable so should still behave the same.[/

Try moving the kickdown cable a notch. Durability will be more of a concern than driveability.

 

[holden007]

I have a 75mm on my car, got it off a crashed done up Commodore (brought it very cheap). Better response, very little power difference and more fuel. I reckon 68mm is good enough, but unless you have done major mods, its not worth it. Even though if you did major mods, you'll probably go for the twin body system.