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Ram Air Conversion

To reduce noise in the cabin, Lotus routed the air-flow to the air filter in and out of the engine bay using a U-shaped tube. This effectively reduce noise and air flow into the filter. A Ram Air Conversion (not actually a ram air system, more of a nick name) will re-route and air flow more directly into the air box. This will increase road noise, but supply the engine with increased air flow, increasing performance.

This conversion cost nothing in parts and under an hour in time. The guide shows the conversion being done on a SE, but can be done on all Stevens Esprits. G's and V8 owners will have to look at there cars to see if this is possible.


You will need the following parts:

A new pipe if you screw up!

You will need the following tools:

Flat head screwdriver
Phillips screwdriver



Open the engine bay and remove the engine cover. You can sit in the boot to work on this conversion.

Remove six screw with a Phillips screw driver as shown above. This needs to be done only on the right-hand side of the engine bay. Once the Screws have been removed, carefully remove the covering, revealing the pipes.


You'll see two pipes. One is short and goes from the outside air intake (behind the rear quarter light), into the engine bay. The second pipe is much longer (see picture below) and goes from the engine bay tube into the air box. You can see the pipes above, with the short pipe dropping down and running off to the right and the longer pipe running from the far left, passed the short pipe and off to the far right.


Using a flat-head screwdriver to loosen the jubilee clips from the pipes. There are four to do. The picture to the right shows where the air is forced into the tube passing into the engine bay and back out into the second pipe before entering the air box.


Once the jubilee clips have been loosen enough. You can pull the pipes off the four connections. Be careful not to disrupt anything else as there are other pipes and electrically connections.


You now have two pipes off the car. To complete the conversion you have two options. You can use the long pip to connect from the outside intake straight to the airbox. This allows you to put the system back to it's original design. But this also leaves you with a long pipe going from the intake to the airbox. Effectively slowing down the air flow to the air box.

The other option is to cut the long pipe to fit. Giving you a shorter route for the air to travel. But this mean you will not be able to revert back to the original system. If you decide to cut the pipe, make sure you carefully measure before cutting. If you cut the pipe too short, you'll be needing another! The short pipe is too short to be used in the Ram Air conversion and only needs keeping if you think you might revert back to the old system.

When you've reattached the pipe, you will be left with two open connections. Both to the left/back of the car. This is just a pipe/tube that runs into the engine bay and will cause no ill effect to the running of the car when left open.

I have used the first route. Mainly due to time and light, as I was fitting my exhaust, but it also gives me the opportunity to see if I like it, before cutting the pipe to fit. I'm sure I will be cutting to fit in the near future, but you might like to try it first.

Replace the covering carefully and replace the screws. You shouldn't have any problems replacing this as you now have one less pipe. I didn't weight the pipe, but any reduction in weight is good!



I have now cut the pipe shorter to reduce the air-flow further still. This takes only a matter of minutes to do. I cut the pipe with a stanley knife, removing around 25cm from the pipe. You could possibly cut a little more off, but I didn't want to end up with a pipe too short. You can see in the pictures above how short the pipe is and how much I cut off.

V8 Ram Air

After investigating the Ram Air on a Sport 350, it seems Lotus decided it was a good idea. As it's already been done. Not sure if this is just the Sport 350, or from a certain date. So you'll have to check yours to see if it's been done.


LEW's Verdict

LEW's Verdict is a little difficult to give. When I did this conversion, I also fitted a new Sport Exhaust and Cat Bypass Pipe. So I wasn't able to test the Ram Air on its own. The Esprit sounds and goes brilliantly with these two upgrades, but I'm not sure how much difference the Ram air makes. Others have told me there's an increased flutter on lift off and a possibility of 1-2bhp increase. Noise isn't a problem for me as I also have a dump valve fitted.

Since doing the Ram-Air conversion, I've been able to drive the Esprit a little. What I've notice is a real flutter when the dump valve goes off. Makes a great sound, to add to the valve and the sports exhaust. I'm glad I did this conversion. Makes a great sound track.

You can't go wrong with this conversion. If you don't cut the pipe, you can easily revert to the original set up. With no cost involve and only around 45 minutes of your time. Why not give it a go!

If you do this conversion. Feel free to e-mail me with your opinion on it and I can add it to this page. kato@lotusespritworld.com

Further Modifications
by Travis

This is my drain for the RamAir and as far as I know I'm the only one with it...

The induction silencer box is between the air scoop and the air filter, it is designed like a particle/water trap. And it has a drain hole.
By doing the ram air mod you have no drain, so the water your intake ingests goes into the filter, and engine. Small amounts probably doesn't do anything bad.

But I tend to drive in the rain, though my state of Colorado is very arid and dry compared to England... And I wanted to give the excess water a place to go at the back of the air box, on the outside of the filter.

I mounted it flush, and sealed it with polyurethane adhesive so it is flush with the surface, and then I run a hose down to the ground.

Note: This modification isn't neccessary unless you drive in lots of heavy rain, or tend to aim you hose at the air intake while cleaning.

Just done this one on my '89 SE.Really pleased.Such a simple and the car is now making all the right noises i.e a nice little snarl at low revs and then lots of induction noise (I knew something had been missing) as you accelerate.I am interested to see just how much induction roar I'll get when I pop in a sports filter.Good one - do it. Colin


i have completed the ram air mod today on my 1994 s4. very easy to do (apart from one clip, orientation was very bad) would have taken about 30 mins. but longer due to clip. noticable engine noise, sucking & turbo flutter etc. throttle response is better and pulls slightly better tested up to 130 (private road) and in 5th gear the pulling is a lot more noticible. will be fitting a k&n filter in a week or twoall the best.

UPDATE 28th March 2015
Comparing corrugated (dryer) hose to the smooth duct of the same diameter, the latter creates less flow restriction.
See results of the test here: www.autospeed
(Scroll down to the heading title "Phase 3" and you see the results).
For more details, see www.thelotusforums.com/forums

Considering all of the above, elimination of the corrugated hose increases the turbocharger efficiency and prevents turbo surging. Smooth bore CAI ducts work the best."

Here are some pictures, attached.

John D.


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