What carb? (if any?)

[BenzBoy]

I've finally got a V8 (4.5 Mercedes), but now I have a problem. Because I can't leave anything alone, I'm considering a few tweaks...

I still want to fit a turbo - I have most of the parts so I might as well! I'm also thinking of junking the injection for carbs of some sort but I'm worried that this will be a backwards step power-wise.

Some of the carbs I was thinking of were...
- Twin Weber / Dell'Orto 45's (expensive...)
- Four 1.75" SU's
- A big Holley or Edelbrock (what kind I have no idea!)

I know absolutely nowt about Holley and Edelbrock carbs but I've seen them on Rover V8's and (besides everything else) they look great.
The main thing here is power, and what will work best with a blow-thru turbo. I think trying to hook up the fuel injection to cope with a turbo is asking too much, and I aint too keen on building a Megasquirt kit as my electronics experience is pretty non-existant!
Any ideas and suggestions welcome!

[Revolution 9]

I'd say you wan't the minimum number of carbs possible, for ease of maintenance and setting up, so maybe the Holley/Edlebrock option? You could look into how the Broadspeed Capri turbos were set up. I think those used what was in essence a single carb in a metal box of some kind, which was then connected to the turbo. Exactly why, or how this helped, I don't know, but apparently it was the best option available. I think the same engine was used in the TVR 3000 turbo models

[BenzBoy]

Good thinking - multiple carbs could get complicated! What I don't want to happen is to get a similar bhp from a carb / turbo setup to the original injection!
I'll look at the Broadspeed setup and see how they do it.
The problem with a lot of Mercs is that there's no aftermarket tuning bits for them, so everything will have to be fabricated from scratch!

[BenzBoy]

Hmmmm... been doing some Googling and now I'm really tempted to get a Holley four barrel.

[GrumpyOldMan]

I would try to use the factory injection system, plus an ERL MF2 controller and a couple of extra injectors...

What injection system does your V8 use ? Jetronic ?

[Paul H]

I'm not a mechanic, or engine conversion expert, but if I was doing the conversion that you are talking about, I would concentrate on getting the engine properly fitted in its standard form. If there is the need to troubleshoot any installation issues, it will be without the added complexity of the tweaks, especially as you say that there isn't much tuning info for these engines. Once happy with it, I'd then start the tweaks, especially since once it is in, then it is much easier to see the amount of space on top of the engine for different carbs etc, depending on whether or not you want to avoid a bonnet bulge .

As for merc engine conversions, back in the early 70s, there was a 'Pagoda' SL fitted with the 6.9 V8 from the 600!! With appropriate gearing to suit the new engine, it would then easily outrun Ferrari Dinos ;D

[BenzBoy]

Psychodriver - The 450 I think is K-Jet, although it could be D-Jet... I haven't had a proper look yet as it's still in storage! Now for a dumb question: what's an ERL MF2 Controller? And could I use cold start injectors as my 9th and 10th injectors?

AmazonSprite - I saw a 6.3 Pagoda on a US site a while back - scarily fast!! I appreciate what you say about getting everything running right before messing with it. It's my fault, I just can't leave things alone!

[TheFrequentFryer]

Austin Rover used Sealed SU's to run the Metro turbos.

In the states, turbo carb engine V8's are more popular, and some firms do ready sealed 4 barrel carbs that just need a bonnet rather than a sealed box.

Worth hunting states side for a ready sealed carb, or something more sealable.

[GrumpyOldMan]

BenzBoy said:

Psychodriver - The 450 I think is K-Jet, although it could be D-Jet... I haven't had a proper look yet as it's still in storage! Now for a dumb question: what's an ERL MF2 Controller? And could I use cold start injectors as my 9th and 10th injectors?

The K-Jetronic can be used in turbo conversions ! There are a couple of websites that explain the way it works and how to tweak it, like the following two :

www.students.tut.fi/~hezekiel/bosch.htm
www.vectorbd.com/peugeot/bosch.html

An MF2 is a very small (and easy to tune) mappable injector driver... It's very popular around here, especially when turbocharging old injection-equipped engines.

You can read more about it here : www.aquamist.co.uk/cp/mf2/mf2.html

I have been told that cold start injectors are not suitable for mixture enrichment during normal running... I think it has something to do with the position and the spray pattern of these injectors, which cause some cylinders to run rich while others run lean.

In general, I've been told that (single) extra injectors should be placed around 30cm before the throttle butterfly, so that the gasoline can evaporate and form a homogenous mixture before reaching the inlet manifold.

I'm sure you can find a couple of large injectors very cheaply in a scrapyard, but flow test them before installation, so that you can be sure that they will provide enough fuel for the engine.

A very nice article on injectors (by Dr. Dave Walker) can be found here : www.emeraldm3d.com/em_how.html