Discussion
quote:
What sort of an increase in torque and power does removing the pre-cats give? Assume this is for all Griff 500s -mine is a 98. Is it an exhaust specialist job to replace with staight section pipes or you are saying take out the contents. Can you recommend who can do this cheaply (Fernie's maybe) or is it a DIY job if you have a 2 ton lift!
Chris
The gains were in the region of 5-10 BHP when I had them taken out of my 4.6. I would expect similar from a 500.
There's no metal bashing involved, you simply remove the cat matrix from inside each manifold. If you're interested, Tower View can then fit a cone where the cat used to live, which increases mid-range torque slightly.
These mods are worth having IMO if you're working on the exhaust, since they give a very cheap power increase (no ECU remap required). But the gains aren't really enough to justify taking the manifolds off just for this.
Cheers,
Peter Humphries (and a green V8S)
Contentious mode on...
My experience with exhaust and cat mods etc is very varied indeed with some cars getting improvements and others not and in all honesty the cars that have gained improvements have either had other types of mods done or have had blocked cats where removal is actually addressing a fault. This makes judging any improvement difficult because there is little before and after stuff around and these engines are also handbuilt with variations. Some gains may also be recovery where the engine was down because of bad tuning or a problem that got addressed when the mod was made so the power gain is attributed to the modification.
The exhaust is less of a contributor to power improvement than people might think. Cats are claimed to restrict power because the impede flow so removing them is a good idea. The TVR cats are probably the best at not impeding flow there are. Removing the cats completely creates a huge expanse in the manifold that causes problems and so constricting this should improve the performance. Several constrictors have been used and but the gains are still not clear if any. Removing pre-cats is a compromise in this respect. As Pete says, not worth doing unles syou are doing other things.
The problem is that engine power gains are dependent on all the relevent engine departments working together. Changing one does not necessarily give you any real gain. Change something else that was restricting the engine and suddenly payback time. The issue is that two things have changed here and it is difficult to attribute the total change to any one. With most engine mods, the ECU will need remapping. Let's say you get 20 bhp improvement. How much is due to the ECU and how much to the latest go faster air filter? In practice you might only get 2 from the filter alone and 10 from the ECU alone but combine them and away you go.
Removing the pre-cats on their own probably won't do anything except improve the response. Do it with an ECU rechip and you may get a bit extra and so on. In other words the full potential of some upgrade parts can only be exploited when they are part of a system upgrade.
Fitting a bigget throttle and chipping will help get more mixture in but this will be limited by the inlet manifold and air flow meter. Upgrade these and the next limit may be the throttle (again). Fit a bigger one and the next problem could be the fuel injectors and fuel pump pressure and so on. In other words, fitting in complete packages is often the safest way to guarentee performance. There will still be some suck it and see because engines do vary in their ability but that is why I believe in upgrading needs to be considered at an engine level or subsystem level.
The trouble is that single component changes can make a big difference but often it is because the rest of the engine is at the next platform level and without these, the change is miniscule. The end result can be a very dissapointed owner.
So do anything and you need an ECU rechip and rolling road session. Without this, other mods can be a waste of time. So that is the minium. Making one mod without following through the rest of the system is potentially a waste of time because not all the benefits can be obtained. So the next modifications need to be done at a platform/subsystem level. Doing it any other way increases the costs and reduces the power gains that can be achieved.
Steve
www.tvrbooks.co.uk
My experience with exhaust and cat mods etc is very varied indeed with some cars getting improvements and others not and in all honesty the cars that have gained improvements have either had other types of mods done or have had blocked cats where removal is actually addressing a fault. This makes judging any improvement difficult because there is little before and after stuff around and these engines are also handbuilt with variations. Some gains may also be recovery where the engine was down because of bad tuning or a problem that got addressed when the mod was made so the power gain is attributed to the modification.
The exhaust is less of a contributor to power improvement than people might think. Cats are claimed to restrict power because the impede flow so removing them is a good idea. The TVR cats are probably the best at not impeding flow there are. Removing the cats completely creates a huge expanse in the manifold that causes problems and so constricting this should improve the performance. Several constrictors have been used and but the gains are still not clear if any. Removing pre-cats is a compromise in this respect. As Pete says, not worth doing unles syou are doing other things.
The problem is that engine power gains are dependent on all the relevent engine departments working together. Changing one does not necessarily give you any real gain. Change something else that was restricting the engine and suddenly payback time. The issue is that two things have changed here and it is difficult to attribute the total change to any one. With most engine mods, the ECU will need remapping. Let's say you get 20 bhp improvement. How much is due to the ECU and how much to the latest go faster air filter? In practice you might only get 2 from the filter alone and 10 from the ECU alone but combine them and away you go.
Removing the pre-cats on their own probably won't do anything except improve the response. Do it with an ECU rechip and you may get a bit extra and so on. In other words the full potential of some upgrade parts can only be exploited when they are part of a system upgrade.
Fitting a bigget throttle and chipping will help get more mixture in but this will be limited by the inlet manifold and air flow meter. Upgrade these and the next limit may be the throttle (again). Fit a bigger one and the next problem could be the fuel injectors and fuel pump pressure and so on. In other words, fitting in complete packages is often the safest way to guarentee performance. There will still be some suck it and see because engines do vary in their ability but that is why I believe in upgrading needs to be considered at an engine level or subsystem level.
The trouble is that single component changes can make a big difference but often it is because the rest of the engine is at the next platform level and without these, the change is miniscule. The end result can be a very dissapointed owner.
So do anything and you need an ECU rechip and rolling road session. Without this, other mods can be a waste of time. So that is the minium. Making one mod without following through the rest of the system is potentially a waste of time because not all the benefits can be obtained. So the next modifications need to be done at a platform/subsystem level. Doing it any other way increases the costs and reduces the power gains that can be achieved.
Steve
www.tvrbooks.co.uk
Hi Joolz
Sorry to take so long to get back to you. You are in fact one of the "clever people" I had in mind when I wrote the post! I'm not too well clued up on the Emerald system, since I haven't looked at it for nearly three years. If you did Graham's system then he's in good hands - his rather brief comment didn't give much away!
The extra torque with airflow meter present is a real oddity. I learnt about this one from John Eales first of all, and it surprised me too. However I have verified it for myself many times since then. You also lose torque if the airflow meter is too big, although there is a balance to be made between metering range and mid-range torque.
Out of interest I have measured the pressure drop on a 20AM (4.6 Range Rover type) meter on a fully modified 5.3 Litre engine running an ACT 78mm single throttle plenum, producing 340BHP (on V8 Developments dyno). There was virtually no pressure drop from filter to inside the plenum. My conclusion was that in this case it is worth having the metering accuracy of the fuelling, since there was no perceptible loss of power. In case you were wondering, yes it did pick up torque with a smaller meter, but it lost power too.
We tried removing the plenum completely, and just running it at full bore (pretty scary to start up)! In this case it lost 40lb/ft across the board!!!
I would love to be able to say I know exactly what is going on - but it wouldn't be true. If it could be measured then we could work out how to get more of it of course! It appears that because the engine cannot be pulse tuned (due to the odd firing order - and unlike a cerbie), so it seems to depend more on inertia. It appears that the meter in some way smoothes out the flow through, and the increased exit velocity helps in some way. This is an intriguing project for future development....
You may find it interesting to experiment with a standard 3AM or 5AM meter. Graham didn't say what the original vehicle was (over to you Graham!), but this would be a good choice. If you do want to go on to forced induction later, please give me a call because I have learnt a lot about this and it would be interesting to compare notes.
This information is only valid for low boost (less than 1 Bar / 15PSI), but you can get nearly 500BHP out of a properly built 4.1 Litre using this anyway. There probably aren't too many transmissions that can take that anyway. I run a Borg Warner T56 gearbox (close ratio version) in my own car, and even that would be struggling! As a personal preference I prefer to use heated element sensing for the fuelling, and MAP sensing for the ignition. Ignition also needs temperature compenstion to make it safe due to the varying charge temperatures. As you know you don't get a second chance on these things.
>> Edited by Mark Adams on Tuesday 1st October 19:35
Sorry to take so long to get back to you. You are in fact one of the "clever people" I had in mind when I wrote the post! I'm not too well clued up on the Emerald system, since I haven't looked at it for nearly three years. If you did Graham's system then he's in good hands - his rather brief comment didn't give much away!
The extra torque with airflow meter present is a real oddity. I learnt about this one from John Eales first of all, and it surprised me too. However I have verified it for myself many times since then. You also lose torque if the airflow meter is too big, although there is a balance to be made between metering range and mid-range torque.
Out of interest I have measured the pressure drop on a 20AM (4.6 Range Rover type) meter on a fully modified 5.3 Litre engine running an ACT 78mm single throttle plenum, producing 340BHP (on V8 Developments dyno). There was virtually no pressure drop from filter to inside the plenum. My conclusion was that in this case it is worth having the metering accuracy of the fuelling, since there was no perceptible loss of power. In case you were wondering, yes it did pick up torque with a smaller meter, but it lost power too.
We tried removing the plenum completely, and just running it at full bore (pretty scary to start up)! In this case it lost 40lb/ft across the board!!!
I would love to be able to say I know exactly what is going on - but it wouldn't be true. If it could be measured then we could work out how to get more of it of course! It appears that because the engine cannot be pulse tuned (due to the odd firing order - and unlike a cerbie), so it seems to depend more on inertia. It appears that the meter in some way smoothes out the flow through, and the increased exit velocity helps in some way. This is an intriguing project for future development....
You may find it interesting to experiment with a standard 3AM or 5AM meter. Graham didn't say what the original vehicle was (over to you Graham!), but this would be a good choice. If you do want to go on to forced induction later, please give me a call because I have learnt a lot about this and it would be interesting to compare notes.
This information is only valid for low boost (less than 1 Bar / 15PSI), but you can get nearly 500BHP out of a properly built 4.1 Litre using this anyway. There probably aren't too many transmissions that can take that anyway. I run a Borg Warner T56 gearbox (close ratio version) in my own car, and even that would be struggling! As a personal preference I prefer to use heated element sensing for the fuelling, and MAP sensing for the ignition. Ignition also needs temperature compenstion to make it safe due to the varying charge temperatures. As you know you don't get a second chance on these things.
>> Edited by Mark Adams on Tuesday 1st October 19:35
Hi..
The car is a fairly standard 4ltr Chimaera
running with no cats and the emerald ECU.
Its still Got a dissy at the moment ( locked advance) and the next job is to go dissy less.
My long term aim is to go Supercharged rather than bigger capacity, and preferably run the blower through a clutch ( too much watching mad max as a kid). that gives us a problem with getting the car to run on and off boost.
We were only thinking of low boost levels to keep the car reliable and usable.
I was thinking of somthing like a powerdyne or a vortec blower, as they look easier to install in the engine bay ( and there is a kit available for a discovery!!)
Id be very interested in you suggestions on what to do with the rest of the engine as at the mo its standard.
500bhp is probably a lot more than i was thinking and extra 100 was probably closer to my aims..
The only problem i have at the mo is trashing the tasmin at mallory on sunday ;-( so budget is a bit depleted..
G
Im also looking into replacing the t5 with a t56... what are you running that box in?
>> Edited by Graham on Friday 4th October 19:20
The car is a fairly standard 4ltr Chimaera
running with no cats and the emerald ECU.
Its still Got a dissy at the moment ( locked advance) and the next job is to go dissy less.
My long term aim is to go Supercharged rather than bigger capacity, and preferably run the blower through a clutch ( too much watching mad max as a kid). that gives us a problem with getting the car to run on and off boost.
We were only thinking of low boost levels to keep the car reliable and usable.
I was thinking of somthing like a powerdyne or a vortec blower, as they look easier to install in the engine bay ( and there is a kit available for a discovery!!)
Id be very interested in you suggestions on what to do with the rest of the engine as at the mo its standard.
500bhp is probably a lot more than i was thinking
The only problem i have at the mo is trashing the tasmin at mallory on sunday ;-( so budget is a bit depleted..
G
Im also looking into replacing the t5 with a t56... what are you running that box in?
>> Edited by Graham on Friday 4th October 19:20
Gassing Station | Chimaera | Top of Page | What's New | My Stuff