Chimaera Tuning - More Questions

[roadsweeper]

OK, following on from my previous post on this topic I'm trying to develop a better understanding of the tuning options available to me for my 1999 TVR Chimaera 400 (28,000 miles). Initially I'm concentrating on exhaust mods because they are relatively cheap and I want the car to sound good for summer when I can get the roof down!

I'm putting everything I have found out in this post in the hope that people might find it useful when they come to do similar stuff.

The following have all been very helpful in my research:

Shane at SFR Engineering in Stockport, Cheshire (www.sfrengineering.co.uk)
John at JP Exhausts in Macclefield, Cheshire ([e-mail])
Jools at Joospeed in Chesterfield, Derbyshire (www.joospeed.co.uk)
Mike at Austec Racing in Crawley (www.austec.co.uk)

Thanks guys!


So, back to the mods. Any mods I have done I'd like to:
(a) Get maximum bang per buck
(b) Be conducive to further tuning
(c) Leave my car able to pass its MOT
(d) Sound better!

As I understand it, these are my options:

(1) Have my existing exhaust silencer sleeved so that the gases pass straight through (£141 inc VAT from JP Exhausts)
Sounds fantastic
Cheap
Probably won't get me any more power
Won't help to get maximum benefit from future tuning
Leaves me unable to have option 2
Possible problems with track day noise regulations and some MOTs

(2) Removal of pre-cats (£366 inc VAT from Austec)
Likely improvement to throttle response
Possibly more power/torque
More expensive than option 1
Leaves me unable to have option 1
Probably won't sound as good as option 1
Possible problem with MOT emissions?

(3) Fitting of sports silencer (£255.57 inc VAT from SFR Engineering)
More free-flowing than option 1
Potential power/torque gain
Will complement a Mark Adams chip and tune at a later date
Cheaper than option 2
More expensive than option 1
Probably won't sound as good as option 1

I know that options 1 and 2 are mutually exclusive, but can options 2 and 3 be done together - if so I would imagine that this would be extremely free-flowing and sound fantastic?

What is the best option, or ocmbination of options, to give the best return from a Mark Adams chip and tune at a later date?

Finally, if I do spend any more money on the Chimaera after the above, it would probably be on suspension and brakes.

Thanks everyone - answers to the questions above and general opinions would be much appreciated and I hope this info is helpful for others out there.

[roadsweeper]

shpub said:

Playing with the exhaust will simply change the note/loudness and not give you any extra power on its own. End of story.

Hi Steve

You must have been replying to my post whilst I was replying to yours on the rollbar thread!

I'm surprised by what you say. My understanding is that using a more free-flowing (better tuned) system can potentially liberate a bit more power, though probably not enough for it to be noticeable on the road.

More importantly, I certainly think that a more free-flowing system will be benefical once the car has been chipped and tuned afterwards, but I suspect we don't disagree on that point?

Cheers.

roadie

[roadsweeper]

Corin Denton said:

I have had the sleeving conversion done by Peninsula and it works a treat, I have considered removing the pre-cats as well and as far as I can gather I wasn't aware you couldn't do both? Who told you this? The noise levels do not come into MOT in any way shape or form so that's one less worry. As far as trackdays go you can buy or rent clip-on silencers to get you on the track. Hope this might help.

Hi Corin

Thanks for the info on silencers.

I was told by Mike at Austec Racing that the silencer sleeing/pre-cat removal are mutually exclusive. I've just gone back and re-read the email he sent and that's definitely what he said, but I guess he could have mis-read the question if you've heard differently from somewhere else?

[roadsweeper]

Corin Denton said:

One word of warning though! When going into town you will find yourself complulsively drawn into multi-story car parks to let the decibels set off car alarms!

Sounds like a nightmare!

[roadsweeper]

MOD500 said:

Have no pre-cats, and running standard exhaust; sounds quite peppy but not over loud (relatively of course ) When I had mine tweaked by Mark Adams I asked him whether sports / louder exhausts make any difference to power, he said in his experience they made no difference at all. HTH MOD. >> Edited by MOD500 on Monday 22 March 14:25

That is extremely interesting. There can be no doubt that a properly tuned exhaust system can add power when the engine is tuned to suit since it is rare for manufacturers to produce exhaust systems that are so good that no significant power gains can be made (though I believe standard bikes exhausts are incredibly good).

My guess is that Mark was referring to louder exhausts (al la Max Power types) rather than properly tuned systems. Or, he could have been implying that the standard Chimaera system is so good that aftermarket systems are not significantly more free-flowing.

I think the same issue applies to peformance air filters. People often stick them on their car (usually a 1.0 Nova) and expect a performance increase. In my experience, such filters can give better performance, but the engine/fuelling really has to be set up to take advantage of the greater quantities of air they can induct.

Any opinions?

[roadsweeper]

MOD500 said:

I think I asked Mark Adams about sports exhausts and not about modding the standard system. It has been said on some threads that certain mods to the standard exhaust can actually lose some engine power, due to decreased back pressure or something....shpub is the man to answer such things I reckon

Yeah, I can't see that being a one way street though, if you can make the situation worse than it comes as standard then you can probably make it better.

MOD500 said:

The chip upgrade is well worth it BTW, especially when combined with an induction upgrade. If you are thinking of doing lots of modding in stages, it is well worth planning the sequence of your mods carefully or you could end up having the have the ECU chip updated on the rolling road more than once which can get expensive. HTH MOD.

Yeah, definitely. I'm trying to work everything out up front, but it's quite complicated!

[roadsweeper]

shpub said:

The Rover V8 is a strange engine as it seems to like a bit of back pressure. The idea of tuned exhausts etc do not seem to apply. I am sure that given enough money that some improvements can be made but it is not really cost effective. Decatting (all the cats) does allow some more agressive fuelling to be done which will give a bit more power but usually at the expence of emission failures at MOT time. The 520 has fractured/destroyed exhaust systems and surprisingly does loose a bit of power when the noise increases as a result. Its pull and grunt is restored when the exhaust system is sorted out. I have modified it though by adding an additional small silencer to the output of the standard big bore box. Yes adding a second silencer did help! As the engine is producing 400+ real bhp the exhaust doesn't appear to be much of a limitation. Had to do it as the car was hitting 117 db! It now comes in at around 104-5. I have heard/know of a couple of cases where power has been lost with a modded exhaust but it is very dependent on the car. If you want it louder then a straight through is the way but be aware excessively noisy cars are illegal and plod have been known to pull people over as a result and issue an order against the car. Mainly max power types but something to think about.

Cheers, very helpful.

Essentially then, my choice is probably between option 1 (sleeved silencer) and option 2 (de-catting). I think I might just got for the sleeved silencer. Then later an improved induction system and Mark Adams chip and tune. That should get me up to around the 240 (real) bhp mark I think.

[roadsweeper]

JonRB said:

Of course the best modification for a Chimaera 400 is to sell it and buy a Chimaera 500.

That's actually a very good point. I am also considering just selling mine and getting a 500. The trouble is, they're quite hard to find in the spec I want (<25,000 miles, ideally imperial blue, with a nice interior).

Anyway, even if I get a 500 I suspect the exhaust mod will still have to be done.

[roadsweeper]

shpub said:

JonRB said: Of course the best modification for a Chimaera 400 is to sell it and buy a Chimaera 500. ACtually it is to sell the Chimaera and buy a Griff.... any Griff

Heh heh, now you sound like Pete!

Some people seem to think I'm crazy, but I actually prefer the looks of the Chimaera, though I do think the Griffith is stunning.

[roadsweeper]

rev-erend said:

roadsweeper said: shpub said: The Rover V8 is a strange engine as it seems to like a bit of back pressure. The idea of tuned exhausts etc do not seem to apply. I am sure that given enough money that some improvements can be made but it is not really cost effective. Decatting (all the cats) does allow some more agressive fuelling to be done which will give a bit more power but usually at the expence of emission failures at MOT time. The 520 has fractured/destroyed exhaust systems and surprisingly does loose a bit of power when the noise increases as a result. Its pull and grunt is restored when the exhaust system is sorted out. I have modified it though by adding an additional small silencer to the output of the standard big bore box. Yes adding a second silencer did help! As the engine is producing 400+ real bhp the exhaust doesn't appear to be much of a limitation. Had to do it as the car was hitting 117 db! It now comes in at around 104-5. I have heard/know of a couple of cases where power has been lost with a modded exhaust but it is very dependent on the car. If you want it louder then a straight through is the way but be aware excessively noisy cars are illegal and plod have been known to pull people over as a result and issue an order against the car. Mainly max power types but something to think about. Cheers, very helpful. Essentially then, my choice is probably between option 1 (sleeved silencer) and option 2 (de-catting). I think I might just got for the sleeved silencer. Then later an improved induction system and Mark Adams chip and tune. That should get me up to around the 240 (real) bhp mark I think. 240 bhp .. think you might be a bit high there..

Yeah, it's possible. I based my estimate on reading Tower View Racing's website. Apparently a typical 400 makes 200-210bhp. Figure in improved induction, a chip and tune and 240bhp might be on, particularly if you're starting from 210bhp. I certainly wouldn't stake my house on it though.

[roadsweeper]

N17 TVR said:

HarryW said: Not unobtainable, by a long chalk, however it will never have the torque the bigger engine can give you. It will rev more sweetly and could be considered to be a better engine for road use in some peoples eyes . Rev having seen your beast on the rollers the week before last, I can confidently state there are 4ltrs out there putting similar power out , but then again not the torque. Harry I guess its what you need / want the car for, personally I have yet to be in the position where I thought I really NEED another 1000cc. I have got a 4.0 HC and spent all my Mark Adams money on a) smoothing out the power curve b) regaining any 'leaking' power c) making the car much smoother to drive as the higher cam made it a tad lumpy. Unless you are either a) a real track day demon or b) a traffic light Schumacher c) constrained by a small penis and/or an inferiority complex it should be enough. There is always something quicker than yours....... p.s. and yes I did have my exhaust done because it helped compensate for option C) above

Well, personally I'd just like a bit more performance from my Chim and adding an extra litre might be the most cost effective way to do it. My main gripe with the car currently is that the acceleration really drops off into three figures and it's a bit lumpy at low engine speeds. Of course, it also doesn't feel particularly well planted into three figures, but I can't really do much about that at the moment.

I also see the benefits of having smoother performance and better throttle response, so it's really a case of weighing them up against each other. Plus, I'd really like the car to sound even better.

Oh, and for your information, my inferiority complex is because of my small tackle, so there!

[roadsweeper]

Cosmoschick said:

roadsweeper said: Some people seem to think I'm crazy... Err... As in contemplating a Tuscan in a colour other than black! Look, get yourself down to Austec in sunny Sussex and I'll buy you a coffee while you wait for your Chim's mods to be done and mine to be serviced! And the main topic of conversation...why black Tuscans of course!

Heh heh, why do I get the feeling you're used to getting your way Roz?

Talking Tuscans over a coffee sounds good but it will be a while before I make a visit to Austec I think. I use SFR Engineering in Cheshire for my servicing (Shane is just down the road and does a good job) but I don't think SFR have a rolling road so I might well travel down to work (London) in the Tiv sometime and nip over to Austec for a tune up!

[roadsweeper]

RichB said:

Roadsweeper - quick question, what do you iunderstand the difference between a "sleeved exhhaust" i.e. sprts exhaust conversion and a sports silencer? O wpould have thought they were the same? Rich...

This was a mistake in my earlier post. The sports box conversion SFR Engineering offer is actually a modified (i.e. 'baffling reduced') standard box.