Do I need cats?

[yabadaba]

Looks like the driver side catalytic convertor on my 2001 Z28 Camaro is on its way out. Does anyone know whether I definitely need to have cats fitted, as I'm tempted to use this as an excuse to get a pair of long tube headers and a replacement y-pipe and just say goodbye to the cats?

[ATTAK Z]

yabadaba said:

Looks like the driver side catalytic convertor on my 2001 Z28 Camaro is on its way out. Does anyone know whether I definitely need to have cats fitted, as I'm tempted to use this as an excuse to get a pair of long tube headers and a replacement y-pipe and just say goodbye to the cats?

Isn't it something to do with the Cats being original equipment on the car?

[chevy-stu]

Depends how friendly you are with your mot centre... (I'd dump the cats and get the headers personnaly but I am a rebel !)

[300bhp/ton]

All petrol cars after 1993 had to meet stricter emissions standards. There is no law saying it must have a cat. However the chances of passing an MOT or roadside emissions test without one are very low indeed.

Cars registered after March 2001 have to meet 'x' CO2 levels. I'm not entirly sure if all cars are included in this, but that's how it reads.

Personally I'd say getting rid of the cats is a waste of time. Very little HP to be had in reality and chance of failing an emissions test (MOT or roadside). And you may end up having to re-fit them just for the MOT which is a pita.

You can still run Long tube headers and a catted Y pipe. Most of the Y pipes use high flow ceramic cats with a 3" inlet/outlet. These are generally fine in terms of flow to offer over 400bhp without any restirction. From there on it won't suddenly cost you 100hp either, it will just be a few here and there. I suspect no more than 20bhp (probably more like 10bhp) even at 500bhp levels.

If you want the best of the best then metal matrix cats are the best and will flow, resistance free upto around 550bhp on a V8 (one cat per bank). But they cost a lot.

If you are on a budget the headers to get are Pacesetter ceramic coated long tube headers. Then get the TSP catted Y pipe.

If you have more money to spend then either Kooks or QTP stainlees steel long tube headers are the ones to get, also with a catted Y pipe.

TSP = Texas Speed and Performance http://www.texas-speed.com/shop/

- a very good speed shop, happy to ship to the UK too.

If you want more Fbody advice head over to www.ls1tech.com

[yabadaba]

Thanks 300bhp/ton...that makes very interesting reading. I'm pretty sure that I will go with long tube headers and a catted y pipe. Thanks for the link, too. I'll be taking a look at Texas Speed & Performance...there's soooo many parts suppliers over in the US, but I've found many don't ship to the UK and it's not always clear what kind of reputation they've got, so it's good to get a recommendation. I've mainly been using Summit up to now.

[300bhp/ton]

yabadaba said:

Thanks 300bhp/ton...that makes very interesting reading. I'm pretty sure that I will go with long tube headers and a catted y pipe. Thanks for the link, too. I'll be taking a look at Texas Speed & Performance...there's soooo many parts suppliers over in the US, but I've found many don't ship to the UK and it's not always clear what kind of reputation they've got, so it's good to get a recommendation. I've mainly been using Summit up to now.

The guys at TSP are very good. And have a great reputation (as far as I know anyhow).

Yes there are loads of mods that can be done. A catted Y pipe will cost more money, but I think in the long run it will be less hassle and you won't be swapping parts for MOT tests. The hp loss is not noticable.

You seem to be getting the right bits though. GMMG is a superb catback. The SLP lid should work good too.

Depending on what you want from the car there are several modding routes to go. Namely:

-bolt on only
-n/a
-nitrous
-Forced induction

Most cross over with parts though.

Here are some recommendations I'd look at:


The 4th Gen Fbody has to weak points.

1. The 10 bolt rear end. They have been know to break even with a stock motor. If you plan on big power and big grip and hard launches then chancea are it will break. The good news is auto's tend to be kinder to it so get away with more. On a stock or mildy modded vehicle it's not a thing to worry about though.

The answer is switch to a 12 bolt rear end. Moser and Strange both offer replacement axles. But both are expensive (about £2.5k then you need to ship it and fit it). There are other options, but generally more expensive.

2. The autobox. It's shame GM opted for the weaker 4l60e and not the 4l80e tranny. Lots of people have failed tranny's. But usually on higher hp setups. Infact on what I've read/researched most failures occur when people up the rpms. This sadly means that a cam swap becomes a lot more pricey/risky for an automatic.

There are some things we can do to help out the tranny. first off fit a tranny oil cooler and a Transgo shift kit (only the Transgo, not any of the other shift kits). This should help with the line pressure when shifting (which causes most of the issues).

Lastly, tune the car with respect to not upping the rpm limit.

If you really want a big cam and 6700rpm red line, then a built tranny is your easiest and best bet. But again it's a lot of £££. Once more there are other options, but they are more hardcore.

Bolt on parts:


Headers:

Unless you plan on a supercharger or turbo go for long tube headers. Any other kind will not be of benefit (I'll explain if you want me to).

When you fit LT's you'll either need to tune out the rear O2 sensors with some software or use some O2 elminiators (most paces sell them, they just tell the ECU they are still connected).

Also look at buying some new GM metal exhaust manifold gaskets when you fit the headers. The paper ones supplied are known to be rubbish and blow after a year or so.

Some people have issues with large aftermarket Y pipes fouling the underside of the car. The easy fix is to use poly motor and tranny mounts. There is also a Y pipe hanger worth buy from Mufflex. All of these can be bought from Thunder Racing http://www.thunderracing.com/

I believe they will ship to the UK, but have found them less helpful than TPS.


Intake:

You need to find out what year Camaro you have. Teh 2001/2 models have the LS6 type intake manifold. This is a very good manifold and offers around 20rwhp over the older Ls1 type manifold. If you have the LS1 type, then £450 dollars will get you a LS6 manifold. Combine this with a ported throttle body (do it yourself or buy for $100 exchange) and you should see decent gains and imrpoved throttle response. If you plan on more serious mods hold off on this and look to aftermarket manifolds. The FAST 90 or 92 is very good, but a lot of $$$. The Professional Prodcuts Typhoon is well priced, not as good as the FAST but will see gains over a LS6 type. You'll need a new TB to go with it though.

Other bolt on mods worth looking at are:

underdirve pulleys - these reduce load from the accessories on the engine. Some auto's have battery chargin issues with them though, but most are ok.

electric water pump - I'd probably leave this to last, or unless you don't want to break into the engine. Quite pricey but people have had good results with them.


Transmission/rear end:

Fitting a high stall torque converter will change how the car drives. I'd personally stick with Yank Converters as they are good, will ship to the UK and offer good customer service.

http://www.converter.cc/

There is a lot of good info explaining what a converter does on their website.

Personally I'd look at a 3500rpm stall, anything less is probably not worth the hassle of swapping.

You can also change the final drive gears. Stock is 2.73:1 with an optional sports gear of 3.23:1. Most people will swap to 3.42:1 or 3.73:1 depending on how much you are prepared to sacrifice in terms of terminal speed in gear and crusing rpms. The short gears (higher number) will offer the best accelaration.

If you want to see the affect on speeds/rpms have a look here (select the 1998 A4 Fbody):

http://www.f-body.org/gears/

Chassis:

I personally like the stuff made by UMI Performance.

Lots of very well made parts. The body mounted Torque arm looks a good bit of kit, but probably more for the serious 1/4 mile racer. The Lower connectin arms, sub frame connectors, strut tower brace and panhard rod are all good buys.

Suspension:

However if you want the best in handling, I'd go here for yuo're suspension and chassis requirements.

Strano Performance parts: http://www.stranoparts.com

Look at handling pack 3 or 4 and buy the other bits you need from UMI Performance.

Brakes:

Thunder Racing offer a big brake kit.

http://www.thunderracing.com/catalog/?action=vshop...

It's about £500 and worth the money. If you want to track the car there are bitter setups, but they'll cost you 4 or 5 times more.

There are loads of other bolt on mods, from light weight driveshafts to ignition kits. But most won't yeild any really benefits at this level.

The last bolt on type mod is tuning. In fact you'll actually get very little gains from tuning, although with the exhaust/induction sorted it will help.

Where you really need the tuning tools is for gear selection. By adding a shift kit and a stall you'll encounter a thing called torque management. This limits engine torque in 1st and can cause issues. It needs to be disabled. You may also need to sort out the converter lock up point to. Plus as mentioned earlier, you can tune out the rear O2 sensors.

The software to look at is EFI Live or HP Tuners. Bother very good, but not cheap. In the US speed shops have them so can make these small changes for you, so far I've not found anyone in the UK with them.

[b]n/a tuning:[/n]

Here you have two options, get more displacement or upgrade the internals.

You can buy a stroker kit for the LS1, to tak eit from 346ci to around 383ci. However it's a lot of money and work. you can even buy bored and stroked motors of up to 454ci if you want. But they are all big money and unless youhave a need to do this, I probably wouldn't.

So it comes to heads and cam. This is a very common swap in the US.

However here we hit the issue of the automatic gearbox. Most cams worth buying will all make PEAK HP higher inthe rpms and will want to rev. This means the stock tranny will probably not like it.

You could go for a milder cam and limit the rpms to stock, but you won't then see the full benefit of the swap. So you'll spend money for less gain than you should really get.

If you do go this route, then you can go cam only. Some guys have made great power, but there is a limit.

Personally I feel there is little point adding a small to medium cam. The gains will be limited, yet it will cost the same and have very similar risks.

TSP do some nice cams, the Torquer V3 is the smallest I'd personally look at. The Magicstick 4 is a very poweful cam but a tad too racey for some. With any cam you'll need at least a 3500 torque converter and swap the final drive gears.

There are a lot of good head options. For $800-1000 a set of CNC Ls6 heads are your best bet for n/a. To really see any substantial gains over these you need to spend about $2500 on heads.

There is little point in swapping heads with the stock cam. Lots of work and not much return.


Forced Induction:

This is the sexy option. Running an ATI Procharger blower to a turbo setup does sound fun. But they are expensive. And unless you are preparred to spend money on the motor I'd say this is not the best or cheapest way to these levels of HP.

A company called EPP do some nice supercharger kits and on a stock motor should see 500-550bhp. But they'll cost you around $4000-5000 for the kit. There are cheaper ways to get this. The only good thing is it retains the stock rpm limits, so the autotranny may well get on better with an FI motor making 500bhp but only revving to 5800-6000rpm rather than a n/a one making 450bhp but revving to 6600rpm.

Turbo kits are a lot more money and more of a one off type of setup.

There are remote/rear mount turbo setups from companies like STS. These mount the turbo at the back of the exhaust, under the rear bumper. They have seen good results and cost far less than more traditional front mount setups. But I feel the way they deploy the power is more suited to the US roads and drag strips and wouldn't bode so well on UK roads.


Nitrous oxide:

I leave this until last because I feel it is the best way to get big power from an auto LS1. I know in some circles nitrous has a bad name, but it's really not deseerved.

A stock Ls1 will handle a 125 and 150 shot of nitrous (some even spray a 200 shot, although I wouldn't). And you can get all this extra grunt installed for only £1500. A lot cheaper than a supercharger kit.

The only real downers are, constant running costs. Power not available 24/7 and no improvement to part throttle performance.

But combine nitrous with other mods and it becomes the icing on the cake should you need it.

For nitrous oxide go here (UK company): http://www.noswizard.com/



Building a street car in the UK I'd personally do this:

-sort out brakes, suspension & chassis
-Add bolt on's such as full exhaust, induction and intake
-Add oil cooler and shift kit
-underdrive pulley
-3.42:1 fnial drive gears
-3600 stall
-EFI Live tune
-nitrous oxide kit with a 150 shot

Off the juice it should stop and handle as well as any other car on the road and have enough poke to scare a Aston Martin V8. Should you need it, a flick of a switch will give you enough poke to stick with (or pass) a Ferrari F430.


Sorry for such a long post but I had a lot to say. If you want anything, just post up and I'll try and do my best to help

[yabadaba]

Don't apologise about the long post..that's all great info..thanks

Right at the end you say what you'd do for a UK street car and that's pretty much the route I'd like to go too. Essentially I want more performance, whilst retaining a degree of practicality and not with phenomenal cost. The practicality bit is fairly important because I like to use my Camaro as my daily driver and not just as a weekend car. So I'd probably shy away from something like a high lift cam. I do have a VW Sharan as an alternative, but which would you prefer to get into in a morning?!? Also I only do around 4-5k per year so fuel costs don't really bother me (seems to be coming down anyway).

Here's a few details on what my car has at present, or soon will have. Essentially, my car is currently completely stock:

2001 Z28 A4
2.73:1 gears
LS6 Intake (no EGR)
Stock single tail pipe exhaust

and I'm waiting for the following to arrive:

GMMG catback
SLP lid (not the cold air kit + not planning to do the free air mod)
17x9.5 TT2 wheels (awaiting arrival - not that hey will affect performance, but will look better than my stock 16" rims!)

I've also got a few regular service parts to fit - just as a routine maintenance thing, because I dont know when these were last changed and/or they are fairly cheap to replace, plus my idle when in drive can be pretty rough so thought some of these might help:

Pair of pre-cat O2 sensors (Denso)
Fuel filter (ACDelco)
Air filter (ACDelco)
K&N Oil Filter
Amsoil 0w-30 fully synthetic oil to replace the non-synthetic in it now
ACDelco Iridium plugs
MSD Ignition Leads
PCV valve
Intake air temp sensor

What I was originally planning on doing next was subframe connectors and a strut tower brace. One of the other guys on here (Luc1fer) had recommended this to me and I was looking at ordering direct from BMR. But, as I seem to have cat issues I will probably now look to getting the exhaust sorted first. The Pacesetter lt's and tsp y pipes that you mention sound interesting. I have looked around on some of the US forums (ls1tech and ls1.com) and I seem to remember people saying that the Pacesetters are a good fit and and at a good price. Yes, I had heard that long tube headers are best, but can't recall why (something to do with air cooling?).

I'm interested in doing something with the gears too, as I've heard that the shorter gears wil make my car feel much more lively. I don't want to go too mad though, as it's quite nice to be able to cruise at low revs, so I think the 3.42:1 that you mention would be about right....or maybe even just the 3.23:1..although that might not be worth the change. I hadn't thought about a stall convertor though. Will look into that some more.

I hadn't thought about the tranny oil cooler or the shift kit either, but both sound interesting. Sometimes I wish the gear changes were firmer and more decisive...is that what the shift kit would help with? I must admit that I am a little concerned about my tranny anyway. Two things really. As I've mentioned before on here it seems to clunk sometimes when I accelerate lightly after the car's just been coasting, as if there is too much play somewhere. Also, there have been a few times following mad moments of heavy accleration where I've slowed to a more sedate pace and noticed that it's been very reluctant to shift gear for a few minutes afterwards. But the fluid looks fine and is at the right level....possible overheating?

As it happens, I actually have HPTuners...not that I really know what to do with it. It just grabbed my interest and I thought it would be good to be able to check for DTC's. That's how I know my cat is on its way out! I think I can use it to 'tune-out' the codes I'd get if I ended up doing away with the rear O2's. I take it you don't fit the rear O2's with lt's and a catted y-pipe?


Again, many thanks for taking the time to post all that info. Hope you don't mind if I run a few things past you when I'm closer to ordering some of the above-mentioned parts

Edited by yabadaba on Tuesday 2nd September 13:59

[300bhp/ton]

yabadaba said:

Don't apologise about the long post..that's all great info..thanks

Ta

yabadaba said:

Right at the end you say what you'd do for a UK street car and that's pretty much the route I'd like to go too. Essentially I want more performance, whilst retaining a degree of practicality and not with phenomenal cost. The practicality bit is fairly important because I like to use my Camaro as my daily driver and not just as a weekend car. So I'd probably shy away from something like a high lift cam. I do have a VW Sharan as an alternative, but which would you prefer to get into in a morning?!? Also I only do around 4-5k per year so fuel costs don't really bother me (seems to be coming down anyway).

Here's a few details on what my car has at present, or soon will have. Essentially, my car is currently completely stock:

2001 Z28 A4
2.73:1 gears
LS6 Intake (no EGR)
Stock single tail pipe exhaust

and I'm waiting for the following to arrive:

GMMG catback
SLP lid (not the cold air kit + not planning to do the free air mod)
17x9.5 TT2 wheels (awaiting arrival - not that hey will affect performance, but will look better than my stock 16" rims!)

I've also got a few regular service parts to fit - just as a routine maintenance thing, because I dont know when these were last changed and/or they are fairly cheap to replace, plus my idle when in drive can be pretty rough so thought some of these might help:

Pair of pre-cat O2 sensors (Denso)
Fuel filter (ACDelco)
Air filter (ACDelco)
K&N Oil Filter
Amsoil 0w-30 fully synthetic oil to replace the non-synthetic in it now
ACDelco Iridium plugs
MSD Ignition Leads
PCV valve
Intake air temp sensor

That all sounds good stuff.

yabadaba said:

What I was originally planning on doing next was subframe connectors and a strut tower brace. One of the other guys on here (Luc1fer) had recommended this to me and I was looking at ordering direct from BMR. But, as I seem to have cat issues I will probably now look to getting the exhaust sorted first. The Pacesetter lt's and tsp y pipes that you mention sound interesting. I have looked around on some of the US forums (ls1tech and ls1.com) and I seem to remember people saying that the Pacesetters are a good fit and and at a good price. Yes, I had heard that long tube headers are best, but can't recall why (something to do with air cooling?).

The BMR stuff is fine. It was really only the fancy body mounted torque arm where I would look else where, but for STB or SFC it's a good bet. However if you are happy with the car, I'd say sort the exhaust out first, then look to chassis mods.

As for LT's, well it's to do with a thing called scaenging. Basically one exhaust pulse reaches the collector and creates a negative pressure in another cyilder (the one on an intake stroke). Thus pulling more air into the combustion chamber.

The longer the primary pipes are the lower in the rpm this will happen. Lt's offer the most appropriate rpm band. The MAC mids work ok with high revving setups and I once heard someone say the shorty headers don't scavenge until around 10,000rpm.

In terms of flow, the stock manifolds are pretty good, even on boosted setups. If you run a supercharger you lose this scavenging affect, so shorty headers will work just as good and do outflow the stock ones. On a rear mount turbo you need high exhast gas velocity, so again stock or shorty is the way.

In short, n/a = long tube and nothing else.

yabadaba said:

I'm interested in doing something with the gears too, as I've heard that the shorter gears wil make my car feel much more lively. I don't want to go too mad though, as it's quite nice to be able to cruise at low revs, so I think the 3.42:1 that you mention would be about right....or maybe even just the 3.23:1..although that might not be worth the change.

You need to check if you have a series 2 or 3 carrier. I'm fairly sure most of the 2.73 geared cars where series 2 carriers, but it's worth making sure before buying.

Personally I don't think you'll get much gain going to 3.23:1 I can never make my mind up which is best to go for. And due to the lack of modifed Camaro's in the UK I've never had chance to experience different setups.

I think a 3.42 is a good compromise with a fairly decent top speed still (in 3rd that is). The manaul cars use a 3.42:1 if you want to have more 0-100mph ability then 3.73 would be the way. Even in the use it's a split decision which works best.

yabadaba said:

I hadn't thought about a stall convertor though. Will look into that some more.

This is one mod I'd love to do but haven't yet had the chance to. People tell me it makes you feel as though you are being shot out of a cannon.

Essentially all it does is allow the engine (or gearbox input shaft) to spin faster than the output shaft on the gearbox.

So if in stock trim you'd accelarate from a roll and you'd be at 1500rpm, what the stall will do is allow the same road speeds but all the engine to rev to 3000rpm plus. With suitable grip it also allows much hard accelaration away from the line. Downside is its more revs more of the time, so may affect mpg and make the car noiser to drive. It can also make reversing and slow speed manovering more difficult.

However if you post up a thread on ls1tech.com and say whats the 1st mod I should to. More people will tell you a stall over getting an exhaust. As you have HP Tuners you shouldn't have any real worries getting it all working.

yabadaba said:

I hadn't thought about the tranny oil cooler or the shift kit either, but both sound interesting. Sometimes I wish the gear changes were firmer and more decisive...is that what the shift kit would help with? I must admit that I am a little concerned about my tranny anyway. Two things really. As I've mentioned before on here it seems to clunk sometimes when I accelerate lightly after the car's just been coasting, as if there is too much play somewhere. Also, there have been a few times following mad moments of heavy accleration where I've slowed to a more sedate pace and noticed that it's been very reluctant to shift gear for a few minutes afterwards. But the fluid looks fine and is at the right level....possible overheating?

I remember one of your other posts. I guess it could be slack in the propshaft or diff.

I'd happily take you out in my for comparison (not sure where you are though), I'm near Milton Keynes.

The oil cooler is a good bet and will just help the tranny out no matter. The shiftkit gives a much firmer and quicker shift (should be more responsive too), plus gives greater manual control to properly lock it in gear. And it sorts out some of the line pressure issues the 4l60e suffers from.

yabadaba said:

I take it you don't fit the rear O2's with lt's and a catted y-pipe?

Correct. Easiest thing for you would be to delete the codes via HP Tuners. I'm not sure how to do it, but there is a section on ls1tech.com just for tuning and software stuff.

yabadaba said:

Again, many thanks for taking the time to post all that info. Hope you don't mind if I run a few things past you when I'm closer to ordering some of the above-mentioned parts

Anytime

Edited by yabadaba on Tuesday 2nd September 13:59

[Tadek]

You guys are full of knowledge and wisdom when it comes to car conversions. I only wish that I could have known about your skills earlier on this year.
My problem is with the Corvette C5 Z06 - Supercharged, which I imported from the USA earlier this year. Lots of conversion work was done on the car by a company near Bicester and they advised on replacing CATS, as in their opinion they were disconnected. It had long tube headers on it, but minus CATS & silencers. So as to comply with regulations I had S/S silencers manufactured & sports cats fitted by a company in Banbury. But on completion we found that the engine Check Light still came on, fault: Bank 2 Sensor 2. They changed the sensors several times (I think unnecessarily)at great expense.
Recently, I was told that maybe the ECU needs to be reprogrammed, to accommodate the modifications made, which may sort out the Engine Check light. Besides fitting an 02 eliminator, is there anything else which I can do, or do you know a company with more knowledge then the ones mentioned?
Can anybody help me with this problem?

[yabadaba]

I'm far from being an expert on this and am basing my response not on the Corvette lump, but on the LS1 Camaro engine (which I assume operate similarly in this respect), but from what I've heard it's common to see an engine check light with anything other than factory or direct replacement cats. There are several people on here that are more knowledgeable than me, but this is my current understanding on how it all works...

High flow cats, including those installed within aftermarket y-pipes, will be located in a physically different position to the stock cats and this results in the rear O2 sensors returning different values than would normally be expected....hence the code. I think it's all to do with the relationship between the pre-cat and post-cat sensor readings. You refer to sports cats, so I take it that these are what you have.

It's likely that she cats are actually doing their job and that your emissions will be fine, which would be confirmed by an emissions test. But to remedy the check engine light I believe that the relevant code(s) must be 'tuned out' and that is possibly what the ECU reprogramming that you mention refers to. The programming that is referred to involves telling the PCM not to report on a post-cat error, where the default is to light the check engine light. Another method (that you have also mentioned) is to fit O2 eliminators which just fool the PCM by sending it the data that a fully functioning and correctly positioned cat would return.

Edited by yabadaba on Wednesday 10th September 22:33

[LuS1fer]

Friend's C5 Z06 blew it's cats out. It still passes the MOT. It's surprising how good these cars are on emissions.

[Tadek]

yabadaba said:

I'm far from being an expert on this and am basing my response not on the Corvette lump, but on the LS1 Camaro engine (which I assume operate similarly in this respect), but from what I've heard it's common to see an engine check light with anything other than factory or direct replacement cats. There are several people on here that are more knowledgeable than me, but this is my current understanding on how it all works...

Edited by yabadaba on Wednesday 10th September 22:33

Thanks for your input, as you say, these systems operate in similar ways.
Emissions test show that the system is clean, but the Engine Check light is still on. Which causes me concern, as I am going to be unaware, should anything else happen to the engine.