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f1karting

Found useful power gains..

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Ok I got my basic design, I didnt want to change too much so have gone for the same overal length about 32mm but have gone SMOOOTH MAN!!! If I get a chance tomorrow I will turn a couple out and see what they look like :D

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If the proximity of the stacks to the edge of the plenum is causing such high flow restrictions, why didn't Lotus make the plenum deeper ????

Hilly

I can't say, but my '87 has 16mm lips cast into the backing plate to replace the trumpets (although injected cars don't rely on intake velocity to draw fuel like carbs do.

I also added a 1" spacer to the plenum which allows one to open up the diffuser as well. Adding the spacer opens the radius of the charge path and looks to be a lot less restrictive

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Michael,

Thanks for the info. The pic of your engine is fantastic! I remember speaking to you about transaxle conversions and the like, many years ago. At that time you were trying to achieve 350HP. How much HP have you been able to get out of it recently; and do you have any other plans for more?

The idea of adding the spacer seems to be a great idea, but I am wondering if it has increased lag time due to a larger volume that must be pressurized. Have you noticed any difference or dynoed since the change?

It is good to see you on the forum!

Scott,

Should the progression from the front to back be that smooth or should there be more of a 'wall' around the mouth of the trumpet to prevent pressure variations around the mouth from disturbing the incoming air?

Otherwise they are smooooooooth!

Lee

Edited by Esprit Aviation

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Im not sure, Ive tried to make the path from where the air comes in to the plenum and over the backs of the trumpets a smooth path. You are resticted in terms of you need to taper back to get the swrews in for fixing. Im sure the path is an improvement over the sharp edges of the original pressed steel design. The inside angle and from rad are exactly the same as is the length. I have only changed the outside profile as I am sure this is a crap design (but I am ready to be shown otherwise??! doh!) :)

I have just got my copy of "How to build & power tune Webber & Dellorto DHLA Carbs", ready for the rebuild but might also throw some light on the ideas?

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Ok so I just turned four of these bad boys up. They feel really nice and feel smooth and flowing. Im sure they will aid the air flow over from the back where the air comes in from the plenum inlet especially on the two central ones. In the picture you can see how shrp the original one is in comparison :thumbup:

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That original one it the last picture deffo looks different to the NA stacks.

The NA units have less of a radius and are longer, so Lotus obviously did just fit any old thing onto the Turbo.

carbrebuild08.jpg

Hilly

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Maybe but I wouldnt be so sure lol remeber I live near Hethal and know lots of people who have worked there lol :thumbup:

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That original one it the last picture deffo looks different to the NA stacks.

The NA units have less of a radius and are longer, so Lotus obviously did just fit any old thing onto the Turbo.

Hilly

Both my S3T cars have the long (45mm) stacks.. Budz stacks may be the ones used on the DHLA 40??

Edited by f1karting

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They certainly look nice but I have no idea what effect on the engine performance will be. On the IRL engine we tried full radius trumpet entries and they made no difference whatsoever and on that airbox the air comes down the airhorn, hits the bottom, runs up the outside walls and round the back of the trumpets and into the engine.

Be interesting to see any dyno results you get.

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Ferrari F1 cars use variable trumpets, as you can see in this picture. You will have a black trumpet that ends with a bleu seal then the carbon trumpet take over, the carbon part can move up and down.

Anybody can get these pictures now :shock:

That set up would end this discussion :evil:

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Ferrari F1 cars use variable trumpets, as you can see in this picture. You will have a black trumpet that ends with a bleu seal then the carbon trumpet take over, the carbon part can move up and down. NICE...

Anybody can get these pictures now :devil: TELL US PLEASE...

That set up would end this discussion :) AND START A NEW ONE....

Nice pix!! Trick is we only have a small space to work in.. the next discussion would be the design of the "new" airbox and how to control the VTL

Edited by f1karting

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When overhauling the carburetors on my 83 S3 Turbo I found that there was NO trumpets! :D

I was overhauling the carburetors because the Lotus was stumbling, and it is alot better now, but still not perfect. (At least the hesitation seem to be gone now. :P ) How much will the lack of trumpets influence this?

The other question is, what is the difference between 16mm trumpets and no trumpets?

Brandt

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When overhauling the carburetors on my 83 S3 Turbo I found that there was NO trumpets! :D

I was overhauling the carburetors because the Lotus was stumbling, and it is alot better now, but still not perfect. (At least the hesitation seem to be gone now. :unworthy: ) How much will the lack of trumpets influence this?

The other question is, what is the difference between 16mm trumpets and no trumpets?

Brandt

Seems to me that it is likely that no trumpets would be better than the stock ones... If you could simply added a radius plate to the inlet that would be better. However, if you can get some OE 45mm stacks and have them shortened to 25mm that would work 100%.

What seems to be wrong with the running? J

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Jan, I've found some local machine shop to make me 16mm trumpets according to my design, according to the discussion on this thread. I'll post some pics once I get the trumpets.

As for the stumble, I think the best description will be a mis-fire. New sparkplugs and leads made no difference, and the rotor and cap looks very new still. So I'm starting to suspect the coil, as was found in another thread.

The jets are however still as Lotus specified them, and I suspect thus the mixture may be lean. Will I notice problems with lean mixture only at full throttle?

And now for my biggest worry. As far as I can tell, I have a NA head on my turbo engine. I say this because the water plumbing makes sense for the NA head. Thus I believe the setup is as follows:

1) NA head

2) Turbo cams

3) NA inlet manifold

4) NA water pump with thermostat (Also the turbo Y-type thermostat is also still there, thus there are 2 themostats in the system!)

5) DHLA 40 carburettors with Lotus specified turbo jets

6) Turbo exhaust manifold

7) the block say 910, so at least it should be a turbo block, (and hopefully turbo pistons, etc)

So, I know the cooling of the NA head is not that good, but what other problems can I expect?

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Look forward to seeing the trumpets.. as to the other questions, I have no experience with your combination and cant offer much help. I would put in all new ignition, arrange some dyno time to do some runs to get a baseline to see where you are with your setup, and go from there.

Edited by USAndretti42
Removed a huge quote which was the previous post

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Hi Brandt

I had to buy a head for my Turbo G car and got one from a expert place in England called Espritism. I was a little worried that the head may not have been a turbo head as the cast no. on the side had a 907 number. The way to tell is to measure the stem dia. of the exhaust valve. It should be a sodium filled one to disipate the heat and be 8mm. The N/A are 7mm the same size as the inlets. You can check your pistons are right by the shape machined onto the crowns from the parts list, but would be sure if you got a 910 stamped on yor block all will be ok.

Hope this is of help

Buddsy

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Jan,

I obtained one pair of 25mm trumpets on E-bay, but the other ones went off before I realized, so I'm stuck w/ just one pair. If I can find out who made them I'll get another pair. I will try to post a pic of them, so that if you locate some, you could borrow my two for testing.

Lee

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Finally some pics of the trumpets Iv'e had made. They are are 16mm high, but have a nice 10mm radius to guide the air in. Unfortunately I haven't taken the car for a drive yet, so I'll still have to see if they made any diffrence.

Buddsy, thanks for the advice on the outlet valves, clearly I will have to find a turbo head for my car.

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