Exhaust upgrade...

[Big Vern]

Hi folks, ive had an SJ's SS Exhaust manifold and downpipe assembly for a couple of years now. While it did ok as a temporary job its time to upgrade to something better. (I was one of the ones who had some difficulty with fitting (by my garage) which did involve a bit of cutting and welding).

Does anyone have a suggestions where to go next? Its a 1986 N/A S3. Quicksilver is a no and as far as im aware Alunox only make them for the Turbos?

Many thanks folks.
 

[DaveyT]

Brett,

I think Lotusbits do a full stainless system for ours with a larger bore, but it's not cheap.

SWLC have remanufactured the manifolds, but that wouldnt be any sort of upgrade I guess.

Edited July 5, 2019 by DaveyT

[Big Vern]

Hi Dave, 

Ive seen the Lotusbits one up close. Its very impressive but as you say v expensive. I did consider going back to the cast manifold, i still wonder if there wouldnt be much difference going back to standard....

[drdoom]

There are several points I consider important on choosing a manifold for the Esprit:

1) - On performance there seems to be modest room for improvement if engine is near stock tune. Lotus deliver 172-180 BHP from the 2.2 with the cast main manifold as a starting point. Two mates had equipped 907 Esprit with a large bore 4-2-1 fabricated system, finding that agreeable. That was with something like 1 7/8 inch primaries, only tolerable with the 4-2-1 configuration as that scale would just kill the power band in 4-1 layout. That said, a respected American builder supplying top-tier NASCAR and ProStock NHRA teams has held forth at length on the folly of large-bore mindset. I'll attach a link if found, meanwhile I suggest 1 1/2 inch is correct for primaries in a 4-1, not far off in the case of 4-2-1. The summation statement amounts to keeping energy, therefore velocity, high as possible through to the silencer so as to maximize scavenge therefore cylinder fill. This is altogether intuitive in my view and is consistent both with OEM practice in general and with successful tuners for decades. Contrarily, we seem inclined to regard exhaust pressure ( that which motivates flow, in fact ) like constipation, to be improved via an enlarged passageway as if that were logical in the slightest. I suspect the same pretzel logic in play when one loads "flushes" of one kind or another into the oil or fuel.

2 - Proximity to the exhaust side engine mount  on S1/2 cars means attention to heat management. Stainless does not conduct heat as readily as mild or cast, the lighter mass of tubular retains less energy so less cooking of the kit when stationary. Points to consider include insulation wraps and ducting for favourable airflow.

3 - Installation concerns are well documented in a number of threads including one active at the moment in this category. The difficulties described in terms of successfully hauling together an array of 4 separate primaries seem entirely predictable. 

 

Calvin Elston posts.pdf

[PilotSteve]

if anything is found i would be interested dont think sj,s has much perf improvement ???

[Big Vern]

Mine rattles and shakes. I think it was fitted the best it could have been but im thinking now of seeing if someone can fabricate a new one..

[skiing]

I have had the lotusbits one for around 5-6 years now. It sounds fantastic and the car was definitely up on power when fitted. It is quiet on the motorway but sounds excellent on acceleration. Totally changed the sound of the car. It was tricky to fit I believe. It has not deteriorated at all other than some surface corrosion on pipes. Backbox and tailpipe are nice and shiny (I keep them polished). The other pipes do clean up. I recently took the silencer apart (it just rivets together) to replace the packing as it had got louder as the packing slowly disappeared). The only challenge I have is one of the slip joints is a little loose so I get the odd rattle but it is normally fine (Sparky will at some point look at this!). I have put heat wrap around the chassis tubes nearest the exhaust as it is a close fit. It is beautifully made.

[Dan E]

To be fair Henry I can only agree, I followed you up to the 70th, I have to say you are a lunatic, but it did sound lovely 😂

[drdoom]

On 29/07/2019 at 11:52, Dan E said:

To be fair Henry I can only agree, I followed you up to the 70th, I have to say you are a lunatic, but it did sound lovely 😂

Sounds like Henry drives his Lotus as it were meant to be driven😀. The Lotusbits item does look to be well designed, as far as one may tell from the online photo.

[Big Vern]

Do you happen to have any pics Henry? TIA

[mdw]

On 05/07/2019 at 13:27, Big Vern said:

Does anyone have a suggestions where to go next? Its a 1986 N/A S3. Quicksilver is a no and as far as im aware Alunox only make them for the Turbos?

 

Alunox did make 2 HC N/A systems. One for a customer and one as a spare which I bought for my 89 n/a.  I know it was never meant to be a stock item but they may make another although I guess its not an HC engine.

[Big Vern]

Thanks, ill drop them a message

[lotus-62]

mike (from lotusbits)  has the exhaust lenght (prim/sec)  tuned, he race these engines so knows a thing or two about the lenght,  he told me he had a car on the rolling road and played with the lenght untill he was happy.  I have seen them and they look very well made, If I had the money......  

[skiing]

Well I can't possibly comment on driving like a lunatic but I was in a convoy of other Lotus sports cars so had to keep up... ahem... I don't have a picture handy but there is one on lotusbits website of the manifold. The exit pipe is a single rolled lip exit. I would prefer a stock look for this - that is the one change I would make. 

[mdw]

From memory and I may be wrong  one of the pipes on the lotusbits manifold wrapped around the chassis rail rather than the alunox where they all went inside.   Mine  also had a port already welded in for an o2 sensor incase efi was fitted later.  At the bottom of the thread below is  a pic of the alunox n/a system I had.

 

[skiing]

That's right, one pipe goes outside the chassis rail - it is a very close fit. But it does fit.