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Re: GregsVN
Posted: Mon Oct 19, 2015 10:20 am
by immortality
psyolent wrote:yeah me and vlad were talking about it the other day.
i did similar on a vt v6 and lost torque, but, it had twin cats twin muffler and joined before the rear resonator.
i think i will just stick with the Y piece for the meantime.

Shouldn't you be able to retune the timing map a bit to make back some of that torque?
BTW, nice colouring

Re: GregsVN
Posted: Mon Oct 19, 2015 10:28 am
by vlad01
What we talked about was loss when using a full twin system right to the rear as 2ndary scavenging and velocity is lost in such a system.
V6 dont benefit much for a twin system as they are already even firing and nearly all the gains are made at the primary.
with v8 the primaries dont work correctly due to odd firing and they benefit a lot from twin systems with a cross over.
My theory is twin cats and then merge into a single 2.5 from there. The 2ndary collector can actually do its work when the cats are moved before the collector.
Re: GregsVN
Posted: Mon Oct 19, 2015 10:40 am
by psyolent
re: tune.............thats something i didn't do in the VT. it had a 'chip' but whatever that means who knows
zactly right vlad.
thinking about the VS, they had that central cat and one muffler setup. which is interesting. actually i think the VT on are the same too?
Re: GregsVN
Posted: Mon Oct 19, 2015 11:47 am
by immortality
vlad01 wrote:What we talked about was loss when using a full twin system right to the rear as 2ndary scavenging and velocity is lost in such a system.
V6 dont benefit much for a twin system as they are already even firing and nearly all the gains are made at the primary.
with v8 the primaries dont work correctly due to odd firing and they benefit a lot from twin systems with a cross over.
My theory is twin cats and then merge into a single 2.5 from there. The 2ndary collector can actually do its work when the cats are moved before the collector.
I just put a full twin system (LS exhaust) on our L67 VX (already had twin cats and mufflers into single system) and I don't think there been any noticeable loss in low RPM torque.
I'm still yet to play around with the timing but I'm sure there is more to be had then the factory tune gives us.
Re: GregsVN
Posted: Mon Oct 19, 2015 12:00 pm
by Dylan
Could always start with the XU6 tune. I done one for a bloke once on a VY. Used the XU6 timing and adjusted some fuelling and he was very happy.
Re: GregsVN
Posted: Mon Oct 19, 2015 12:07 pm
by immortality
My base tune is The1's enhanced tune which is based on the HSV code
In the lower areas the timing maps are identical between Holden and HSV, it's only at higher airflow and rpm areas it has more timing really from what I can see.
Re: GregsVN
Posted: Mon Oct 19, 2015 12:43 pm
by Dylan
Sounds like a good start then.
Re: GregsVN
Posted: Tue Oct 20, 2015 8:28 pm
by psyolent
i have some work to do with tune. need to learn a bit first. roll on next weekend.
in other news dropped in the radiator, picked up some new hoses and pulled the electric fan apart to paint/clean it up.
been going a bit slow this week, not a good week for sleep

Re: GregsVN
Posted: Tue Oct 20, 2015 8:47 pm
by Dylan
Is the motor modified?
Re: GregsVN
Posted: Wed Oct 21, 2015 5:17 am
by psyolent
dylan, no. its got pacemakers and 65mm TB. no bellmouth. ecotec injectors. so not really.