When Does A Standard 2 Piece 205 Exhaust Become Restrictive?

[SweetBadger 94]

Hi, I'm after some advice for the exhaust on my track based 205.

 

I'm finally getting to the point where I'm going to need to get the car mapped, but want to make sure the exhaust won't be holding it back before I do.

 

Spec is as follows:

 

- Rebuilt MI16 with block decked by 0.4mm (11:1 ish compression)

- Newman PH4 Inlet cam, PH3 Exhaust cam

- Sandy Brown/Colin Satchel inlet (lotus based 45mm throttle bodies)

- GTi 6 injectors

- 4-2-1 exhaust manifold (unknown brand), mated to standard ph2 exhaust (Bosal mid section & genuine pug silencer)

- Dta S40 ECU

 

I got it briefly fired up last weekend, and if I can get my laptop to connect to the bloody ECU properly then will hopefully have the cams run in this weekend, so it'll just need properly mapping.

 

I'm hoping to make around 200bhp with this setup, but one thing I've overlooked is the exhaust.

 

The manifold looks like your standard maniflow 4-2-1 effort so will probably be fine (although diameter of the primaries looks a little on the large size), but will the standard phase 2 exhaust be restricting this engine?

 

I think I read that Maxi was running 216bhp on a GTi6 with some bodies and catcams installed and had a standard exhaust which would suggest that it'll be ok, but that's not saying it wouldn't have made more power with a larger exhaust.

 

I'm not looking for an excuse to spend even more cash on this project (have spent a bloody fortune already!), but if the general consensus is that the a 2" exhaust is too small then it would be daft not to change it.

 

If so what should I be looking at - 2.25" system? And any advice on a place to build / fit a quiet-ish manifold back system in the South London area?

 

Thanks.

[GilesW 41]

My thoughts - the manifold will provide the most restriction, and as you have addressed that I can't see you having an issue at expected power levels.

 

 

I'll be interested in how your engine performs as I am building pretty much the same engine except kent cams 1604 & 03 and 45 jenveys on a colin inlet.

 

So... subscribed.

 

Where are you getting it mapped?

[SweetBadger 94]

Hi, great one vote for not spending more money

 

I would really like to get it down to Sandy Brown for mapping if he can fit me in, but that would mean driving it about 500 miles on the base map - will see how it runs on the map I have (106 gti map pre-loaded from MEF motorsport), before making that call.

 

Otherwise I hear track-n-road are really good and not too far from me, so will also give them a call to see about availability / prices.

[GilesW 41]

The Steve's at Track N Road are excellent (IMHO). Used them many times as have my mates.

A right couple of characters.

 

Obviously Sandy has a very good reputation too.

 

If you use TnR be prepared for a late night, a dodgy kebab from the van (wiser to have a burger), and you'll be making lots of cups of tea.

[welshpug 1,657]

Sandy isn't 500 miles away, but even if it was 5 miles its not worth risking it, borrow or rent a trailer, that way the cold map trim can be done as well as the normal running map.

 

Should be very easily over 200 bhp with those cams, gti6 on 264deg PH2's will get you near 200.

[SweetBadger 94]

 

Well over 200hp would be nice, but don't want to set myself up for a disappointment!

 

So I guess the question should 'be will a standard phase 2 205 exhaust be restricting my engine?'

 

Sorry you're right about the distance more like 300 miles (don't know why but I had 500 in my head; probably because it'd be a 5 hr drive!).

 

Unfortunately my licence doesn't allow me to tow anything over 750kg, so I either have to get there under my own steam, or pay someone to tow the car :-( . Not sure on the likely cost of this but would have thought a 300 mile tow would be pricey!

[welshpug 1,657]

well I bunged "london" and Launceston into google maps, and he's 214 miles away.

 

right car and trailer and you'll be fine, you can tow up to 3.5t MAM, or rope a mate in to do it.

 

 

that or get it shifted by a transport company like shiply, there's loads of guys with small flatbed trucks about, I service for a guy who owns a Saxo rally car who's based near Gatwick and he had is shipped to Colin's workshop for under £200.

 

 

 

Personally I think it will be restrictive, the manifold should be fine, I recall Sarty had the same manifold on his 2.2 at 240 bhp, but an aftermarket freeflow system, specific detail I don't remember but was something like 2.25"

[SweetBadger 94]

 

I was convinced for some reason that having passed in 1999 meant that anything over 750kgs was a no go, but a combined weight of 3500 is doable; with a cat b licence you can:

 

- tow a trailer over 750kg MAM as long as the combined weight of the trailer and towing vehicle is no more than 3,500kg

 

Next mot / insurance time I'll be seriously considering a lightweight trailer and a more suitable towing car!

 

Will look into hiring a suitable trailer and car to tow it with (306 towing limit is too low at £1200 kg), or getting it transported.

 

I'm not worried about the manifold (apart from that it looks a little rough around the edges) but considering the primaries are about 1 3/4 inch and the secondaries close to 2 inch it seems a bit of a drop going down to a 2 inch exhaust.

[Tom Fenton 1,541]

Towing a 205 on a category B is do able legally but requires very careful choice of tow car and trailer.

As you correctly say, 1200kg capacity of a 306 isn't up to the mark.

You need something like 1500-1600kg which usually is mid sized saloon or estates.

However you need to be very careful not to go OTT with the tow car, as your combined weight if trailer & load, and tow car, has to be below 3500kg, and the weight is not kerb weight of the car, but it's plated gross weight.

For e.g. Audi A4 estate, towing capacity 1600kg (tick) gross weight 2050kg. Trailer gross weight 1400kg (400kg unladen, 1000kg load, more than adequate for a 205 plus spare wheels tyres etc for trackday use). So combination is 3450kg which is legal by 50kg!

 

I changed my tow car to a 5 series touring, this threw me over the weight threshold so I did the +E test. So like I say, the tow car needs careful choice. Forget anything 4x4 you are into +E straightaway.

 

You may find it hard to hire a trailer from a hire firm without +E on your license. If you are hiring a beaver tail Transit or similar is a better bet as you can drive it as it's less than 3500kg.

[welshpug 1,657]

what size is the manifold after the collector? the 406 V6 exhaust is something like 2.5" on the downpipe but due to its length its down to 2" at the rear and they're flowing 200 bhp's worth of air.

 

IIRC my BMW is 1800 GVW, can tow 1800 as well, so as long as a 205 & trailer is less than 1700 I'm fine (3500 kg)

 

I have an older 5 series than Tom, so its a fair bit lighter but still rated to tow a good bit

 

Its about the mechanical grip, any LR defender is rated at 3500 kg towing weight, even a 1500kg 90!

Edited October 28, 2014 by welshpug

[SweetBadger 94]

The collector is about 2.5 inch from memory - managed to persuade a standard downpipe gasket over it (had to stretch it slightly), so the mid section is connected via a standard curved 205 flange welded to a reducer.

 

Will keep my eyes peeled for a suitable mid sized saloon - shame to let the 306 hdi go as it's been very cheap hassle free motoring, but needs must.

 

Great suggestion on the beavertail transit Tom - hiring one of those for a day will probably be my cheapest option and the least hassle too.

 

I've heard that the E+ can be quite costly to take and pass - lessons definitely required, and a full driving test with the trailer, how did you find it?

[Tom Fenton 1,541]

I had been towing for about 10 years before I did the +E test so I was very used to the trailer aspect. What was more difficult is as you say, the test is very similar to your car test and you will fail for all the same things, crossing your hands steering, not looking in mirrors enough etc.

I did a 1 hour assessment with a company locally, they recommended for me a 1 day course, 1/2 a day in the morning practising with an instructor, then the test in the afternoon. I passed it first try but without the 1/2 day practise I don't think I would have done, just down to 15 years of driving bad habits.

[camgti 56]

Will all the monies spent so far, spend a little more, get the exhaust done, take it to sandy and smile for a long time!!

 

Most of the hard work is done so to speak, to compromise it now in my opinion would be silly.

 

Cam

[stu8v 68 1 Cars]

As std a Vts has a 2.25" system so thats what I went for.