Exige S soft top and rear clam intake mods complete!

[Needspeed]

Yesterday I did the soft top install mod and at the same time increased the size of the rear clam intake that that flows air to the intercooler. If you are an Exige S owner these mods can be completed relatively easily at the same time. For the soft top install I followed Pilot’s instructions and only varied by using epoxy instead hot glue to secure the grommets. http://www.elisetalk.com/forums/showthread.php?t=27090
For increasing the size of the rear clam intake opening I read the .pdf that Jack had posted and fettled the area described by Lotus Sport. http://www.elisetalk.com/forums/showthread.php?t=33680
I couldn’t believe how much I removed while fettling (see pic). I would say I increased the opening by 20% (1/4 inch)! Both mods are easy to do and only take some patience and time. On thing to note is the fiber glass dust gets on everything so as I was grinding I covered my eves and mouth. I probably should have had an assistant hold a shop vac as I cut and fettled/grinded. Another thing to note is when I went to reinstall my hardtop today, to be ready for the track this weekend, I almost cross threaded the passenger side rear bolt because some of the roof liner fabric got stuck between the screw and the nut. I was turning the bolt in and could tell something was not right so I stopped, pulled off the roof and inspected. I used a razorblade to cut some the fabric back and the screw went in fine. I actually started the rear screws while the top was off, about 3 turns and then put on the top. I found this to be the safest way to avoid cross threading the rear bolts.

Now if the sun would just come out and make the temperature get above 35 degrees I could have some fun!

[mark.r]

Looks like it came out perfect. Good work. I like it.

[Needspeed]

Originally Posted by mark.r

Looks like it came out perfect. Good work. I like it.

Thanks mark, your car is next. Let me know when you want to do the mod. I will gladly help.

[shay2nak]

I've gotta do this too. Did you have any problems with debris going into the intercooler funnel? I wonder how much dirt and crap that will collect over a year.

[wallabyguy]

simply put.....

[tonykomo]

hang on, what's the size of the opening on the roof scoop? and what's the size of the opening behind the roof? surely the roof scoop is bigger so has a "ram" effect and pushes much more air thru the intercooler? also, add the extra drag as well, you must be cutting the equivelent of 20-30bhp from the car. so, what's the point in doing this?

EDIT: I'm referring to removing the hard top, NOT the fettling work.

[Needspeed]

Originally Posted by shay2nak

I've gotta do this too. Did you have any problems with debris going into the intercooler funnel? I wonder how much dirt and crap that will collect over a year.

I actually removed the rubber gasket between the intercooler funnel and the intercooler. I then put a towel below the funnel to catch the debris that fell into the funnel. Once I had completed the fettling I also vacuumed out the funnel with a shop vac. If anyone chooses the gasket between the intercooler and the funnel can be removed easily for periodic cleaning or road debris but I am not sure much of anything will makes its way into the small roof opening.

[Needspeed]

Originally Posted by tonyyoshi

hang on, what's the size of the opening on the roof scoop? and what's the size of the opening behind the roof? surely the roof scoop is bigger so has a "ram" effect and pushes much more air thru the intercooler? also, add the extra drag as well, you must be cutting the equivelent of 20-30bhp from the car. so, what's the point in doing this?

No ram effect here just air blockage as stated by Lotus Sport in the .pdf that Jack posted in this post. http://www.elisetalk.com/forums/showthread.php?t=33680 Lotus Sport claims 20% more intercooler efficiency when you shave the opening. Read for your self and once you remove the roof you will see what they and I are talking about.

[allegretto]

Originally Posted by Needspeed

No ram effect here just air blockage as stated by Lotus Sport in the .pdf that Jack posted in this post. http://www.elisetalk.com/forums/showthread.php?t=33680 Lotus Sport claims 20% more intercooler efficiency when you shave the opening. Read for your self and once you remove the roof you will see what they and I are talking about.

The real question is;

How much will this change auto performance, especially at high speeds and/or track conditions?

I would be very suprised if the airflow wasn't very different through the system. Street drivng may not be any different under most conditions. But under stress it may be a problem. If the intercooler does not sufficiently cool the charge it is possible that the effects would be much like a very hot day. That is, lean mixtures and predetonation. That can lunch an engine.

I do not know the correct answer, but I don't think I'd do this without a discussion with Lotus.

I know it looks cool though, that's for sure.

[qball]

what tool did you use to trim the fiberglass?

[tonykomo]

Originally Posted by Needspeed

No ram effect here just air blockage as stated by Lotus Sport in the .pdf that Jack posted in this post. http://www.elisetalk.com/forums/showthread.php?t=33680 Lotus Sport claims 20% more intercooler efficiency when you shave the opening. Read for your self and once you remove the roof you will see what they and I are talking about.

sorry, not talking about the fettling, I'm talking about removal of the hardtop.

[tonykomo]

Originally Posted by allegretto

The real question is;

How much will this change auto performance, especially at high speeds and/or track conditions?

I would be very suprised if the airflow wasn't very different through the system. Street drivng may not be any different under most conditions. But under stress it may be a problem. If the intercooler does not sufficiently cool the charge it is possible that the effects would be much like a very hot day. That is, lean mixtures and predetonation. That can lunch an engine.

I do not know the correct answer, but I don't think I'd do this without a discussion with Lotus.

I know it looks cool though, that's for sure.

I spoke to a mate at Lotus Sport and he says removing the roof effectively cuts off MOST of the intercooler efficiency. ie, you WILL lose substantial power doing this. yes, it'll feel nice with the roof off but your intercooler will be cooking. i think removing the roof and not placing a larger scoop up there will hurt your performance.

[bgsterling]

Originally Posted by allegretto

The real question is;

How much will this change auto performance, especially at high speeds and/or track conditions?

I would be very suprised if the airflow wasn't very different through the system. Street drivng may not be any different under most conditions. But under stress it may be a problem. If the intercooler does not sufficiently cool the charge it is possible that the effects would be much like a very hot day. That is, lean mixtures and predetonation. That can lunch an engine.

This confuses me. If the "airflow wasn't very different through the system", why would the system cool any differently and lead to lean mixtures, etc..

Regardless, if you assume the adjustment flows more air through the scoop, how does that create a lean situation? The way I understand it, the air scoop is directing air towards the intercooler. The intercooler is cooling the air charge that is being forced into the system by the supercharger. The cooler air charge is more dense so it can mix with more gas. Providing the computer is adding more fuel, which it should be doing based on the readings coming from the O2 sensor, the engine will generate more power. Are you suggesting that fettling the scoop will flow less air?

Please don't take me the wrong way. I'm not picking on you. I'm trying to understand.

[Needspeed]

Originally Posted by qball

what tool did you use to trim the fiberglass?

For the fettling of the intake I used a Dremel with a long and narrow grinding bit. For the soft top grommet install I first used a drill to make pilot holes then enlarged them with the same grinding bit I used to enlarge the intake.

[Needspeed]

Originally Posted by tonyyoshi

sorry, not talking about the fettling, I'm talking about removal of the hardtop.

I agree… I wouldn’t take the car to the track with the roof off. I actually already put the roof back on because I am going to the track this weekend.

[tonykomo]

Originally Posted by Needspeed

I agree… I wouldn’t take the car to the track with the roof off. I actually already put the roof back on because I am going to the track this weekend.

but i guess my main point is do you want to even drive on the road with such a drop in power and efficiency? also, won't the charge air get pretty damn hot and risk the engine stamina over the long run?

from what i heard, lotus assumed if the supercharger was being engaged, then there will be significant airflow to cool the charge air. BUT, if that airflow is disrupted then the supercharger is in fact operating at full pelt but without the right amount of air to the intercooler.

i'd seriously reconsider doing this on an Exige S. a normally aspirated exige won't have any issue but for the S.... i'd say you're taking a big risk. of course, it's your car, your risk... just my 2 cents.

[bruh_la]

Lotus says its ok to remove the roof in the owners handbook. it will reduce the efficiency of the intercooler but the ecu makes sure no damage can occur to the engine.

[caexiges]

I am driving my Exige with top off every weekend - CA. last Sat is was mid 70's and I could not notice a big difference.
From low RPM pull I can definitely confirm the intercooler is working big time - hence "most of the effect" seems very unlikely. Otherwise the car would feel like an Elise at low RPM, right?

Simplest answer would be a measure sprint with top on and off. Anyone done this yet?

[tonykomo]

i think it's more about use over a period of time, not just sprints. for instance, when i drive my exige s, it's for at least 1 hour. all sorts of roads, highways, twisties etc etc. surely with all that supercharger usage and the disrupted airflow, after 1 hour of usage, the intercooler must be pretty hot? would be good to have 2 identical exiges s's, one with roof on and one without, give it some driving over 1 hour and compare. maybe even if the drivers swap over half way thru to see if they can tell the difference.

would be nice to get a definitive answer on this as driving with the roof off is really nice, expecially when's it's crisp and sunny like here in tokyo.

[allegretto]

Originally Posted by bgsterling

This confuses me. If the "airflow wasn't very different through the system", why would the system cool any differently and lead to lean mixtures, etc..

Regardless, if you assume the adjustment flows more air through the scoop, how does that create a lean situation? The way I understand it, the air scoop is directing air towards the intercooler. The intercooler is cooling the air charge that is being forced into the system by the supercharger. The cooler air charge is more dense so it can mix with more gas. Providing the computer is adding more fuel, which it should be doing based on the readings coming from the O2 sensor, the engine will generate more power. Are you suggesting that fettling the scoop will flow less air?

Please don't take me the wrong way. I'm not picking on you. I'm trying to understand.

I understand what you are saying but that is not the issue. It's not the external system, it's the internal system's response to the external change. The reality is that unless you have fuel pressure to spare (and a lot of it) the true fuel/air ratio is somewhat dependant upon the temprature of the charge. As the temp rises, Physics says that the gas phase occupies more volume. The practical outcome is that the spark will be greatly retarded to avoid (or attempt to avoid) the pre-detonation. This will cause loss of power under low load, and possibly worse as load increases. ECU's can do a lot, but they bump up against reality too.

If it is "fail-safe" you'll just notice a drop as temps increase. If it is not...LOOK OUT!