84 replies to this topic

[Jim_Cross]

True, but then there seems to be a lot of variation between cars. Look at Cheeky's results - 7bhp on some people with basically the same mods. This could be partly down to mileage, but also down to some engines putting out more power than others. Same with R1 NUR and his 12bhp-over-standard VXT. Also, you have to bear in mind that each remap is different. I guess it could be the case that under certain conditions, you can end up with a better map than under other conditions. And there's all the other factors, such as the accuracy of losses for your individual car, tyre pressures on the rolling road etc etc. Also, we're only considering peak torque and peak bhp figures. At the end of the day, many of us bought the VX over the Elise because we love the mid range it's got. To get a really good idea of the effect of individual mods, we would really need to compare the power and torque curves of the cars in question. For example, look at the S1 Elise Sport 160...50bhp more than the standard car, but less torque across most of the rev range. So unless you cane the hell out of it, a standard S1 is faster on the road in many situations.

[Jase_MK]

Yeah, I agree that all this talk of peak power and peak torque is pretty meaningless - it's how the car feels across the entire rev range that's important. That's why I bought the VX too. I still think the biggest gains to be had in the exhaust area are from removal of the pre-cat. The main cat may well be the most restrictive part of the system but a sports main cat doesn not eliminate this restriction, it just reduces it a bit (unless you go for a full on cat replacement pipe). A few more results worth looking at (to be taken with a pinch of salt I know, for the reasons you mentioned): NO REMAPS Big_Si (Full Milltek and Viper) - 155 PaulB (Full Milltek) - 155 Cheeky (pre-cat) - 154 REMAPS P11 COV (VX backbox, pre-cat, piper induction) - 170 Ianhd (regal backbox, pre-cat and K&N induction) - 167 PaulB (Full Miltek, ported head) - 169 Big_Si (Full Miltek, Viper) - 170 Robski (Full Milltek, Viper) - 167 I guess what I'm saying is that Milltek/Thorney claim that the 200 cell main cat is what gives their exhausts the majority of the performance gains, and I'm yet to see any convincing evidence of that. If that was the case, you'd expect people with full Milltek systems to be putting out a good 10bhp more than those with just a backbox and pre-cat removed.

Edited by Jase_MK, 23 March 2004 - 12:41 PM.

[clipping_point]

Very true! Why think a sports cat or a injection system gives anything at all if not someone show it!! Thats why I did my table the first time. And maybe time will tell if a ported head is not needed to reach 190 hp, and race cams is.

[Thorney]

Actually thats not what I said....I said the removal of the pre cat AND the race cat is what makes the difference and not the backbox. I've not done any testing with precat in/out cats in/out as when the system is off you replace them both. and to repeat someone else....please stop looking at BHP numbers as if they're some kind of holy grail, driveability is what its about. The concept of a race cat is not to give you big bhp gains but simply to allow the engine to breath better thereby which increases throttle response etc etc. Same applies for other engine work. Lightened flywheel - no bhp but spins up faster making the car more revvy but best used in conjunction with a Gas Flowed head - which simply is a more efficient movement of flow around the engine which means it works well with Race Cams - as these DO increase bhp but only really at higher revs. STOP looking for pub bragging numbers if you want that then get FI or buy a VXT, concentrate on HOW it drives.

[Jim_Cross]

Actually thats not what I said....I said the removal of the pre cat AND the race cat is what makes the difference and not the backbox

Sorry Thorney, that'll be me making stuff up!
Must be getting old...the memory's going

[Thorney]

unlike a lawyer to get these things wrong

[clipping_point]

Look here:
http://www.vx220.org...t=ST&f=9&t=4806

[Jim_Cross]

Me? A lawyer?!
I might have offended you by getting that a bit wrong, but calling me a lawyer, that's taking it far too far!

Editted to say:

Cat
Pre-cat
backbox
pipe routing/size

Looks like my memory is in tact

Edited by Jim_Cross, 23 March 2004 - 03:24 PM.

[Thorney]

LOL at lawyer comment, I'm getting my Jims mixed up Bit unfair on the quote the whole post said: "In order of highest restriction (for NA this is) Cat Pre-cat backbox pipe routing/size For VXT it's: Cat Pre-cat Turbo downpipe backbox pipe routing/size In terms of getting more power but on a budget the order should be: Precat removal (basically free if DIY) racecat backbox You've already done a small part but next pick would remainder of exhaust and then do a chip. Get the engine to breath right first and then make its heart pump harder. " So I did say precat first (due to costs) then cat and on numerous other posts I have combined cat and pre-cat together as a single item. But I tell you what (seeing as I'm being got at here) how about someone put a race cat in but leave the pre cat and see what happens?

[Jim_Cross]

I'm not getting at you John, only joking! I'd be happy to let AmD fit the Milltek with the pre-cat in, rolling road it, then remove the pre-cat and rolling road it...but I doubt they would want to waste their time doing that, especially on a Saturday.

[Jase_MK]

Sorry Thorney, wasn't trying to get at you. If you take just a Milltek backbox with standard downpipe (pre-cat removed) and a full Milltek system and compare the two, any gains on the latter should be entirely attributable to the Milltek race cat. That's why I posted those stats. So for instance: Full Milltek, no other mods - 155bhp precat removed, no other mods - 154 bhp any diff between those two should be down to the race cat alone (assuming the backbox does nothing for power). But then we are back into the whole debate about the reliability of RR results, differing performance from car to car, importance/relevance of peak BHP figures, etc. So we have come full circle. At the end of the day (I hate that phrase), it's all about how it feels to drive, and a big part of that is how it sounds too. So what's good for one is not always great for another - I don't think anyone is ever going to be able to say "this particular modding route is the definitive one for absolute maximum driving pleasure".

[Jase_MK]

And so to answer you original question Lewis (sorry!). If you are happy with your vauxhall sports exhaust and don't want to upgrade to a full system, my own personal advice would be to get the precat out, put a good cold air induction system in (I used to have a Viper, it sounds awesome), then go for a remap. then if you really wanna leave people behind on the twisties, get a good geo setup done by someone like ScaredStiff or even better fit some decent aftermarket suspension. All IMO of course

[Jim_Cross]

At the end of the day (I hate that phrase)

How about "Bottom line..." - definitely worse

[GerryM]

At the end of the day (I hate that phrase)

How about "Bottom line..." - definitely worse

Nah!, being able to 'think outside of the box' is worse er a !

[paulb]

Work on the breathing on mine made it feel much more lively and fun. The lightened flywheel had the biggest single impact on the character of the car, without actually increasing the power at all. It certainly seems the case that Cheeky has one special engine as his made 6 bhp more than mine when I also had the flowed head (I only got 169 at that point). I think mine is still tight (only 5k miles when the work was done) so part of the plan is to get some miles on it this year so that it should loosen and free up a few more horses. The main thing I am after is changing the character of the car, not drag racing. At just over 180 bhp, it is quick enough for now, but probably not always. The things I really like are the lightened flywheel and the fact that the cams make it a bit lumpy at idle so it feels like a proper sports car. Next up is definitely handling as the car goes and stops well enough for 95% of occaisions.

[clipping_point]

Yeah, but I would skip the cold air induction, since it actually is "hot air" (unless you want the sound, which can be quite irritating). Take out the precat (free) a AmD remap (£295) and a geo setup (free, just do the adjustment of toe-in once you´ve removed the shims) And put in a lighter flywheel at some £170. I will!

Edited by clipping_point, 23 March 2004 - 05:23 PM.

[Jase_MK]

The lightened flywheel had the biggest single impact on the character of the car, without actually increasing the power at all.

Would be interested in having a listen/pax ride to check this out Paul. This is something I really fancy. I love that throttle blip characteristic of bike engines that you just don't get on cars as the revs rise and fall so slowly.

[Jim_Cross]

Yeah, but I would skip the cold air induction, since it actually is "hot air"

Is it though? The Viper has a carbon surround inside the cone, the aim of which is to shield the air from the heat of the engine - something not done by the standard airbox. With the air feed for the Viper coming from the vent, I would have thought this would result in cooler air than that provided by the standard airbox?

[Thorney]

The mileage is important. I've just come from AmD (was setting up Ducati996's Nitrons for him) and they'd just done another NA stage 3 (cams, Milltek, flywheel, gas flowed head) and because it only had 1700 miles on the clock came up with 173bhp. Get some miles on these cars chaps...it DOES make a difference.

[jneill]

Get some miles on these cars chaps...it DOES make a difference.

I'm glad Thorney ran that up the flagpole. I salute it.