S1 Mini-Project: Engine Cover Sound Insulation

[Tony K]

Esprit S1 Mini-Project: Engine Cover Sound Insulation

As we know, early Esprits were not the most refined cars in terms of noise and vibration; but Lotus did put forth some effort toward that end. Whatever success they had in making the S1/S2 more civilized, I consider important; the little bit of noise reduction here and there make the car much more pleasant to use, and can make the difference in the whole experience of an early Esprit, between it feeling like an unfinished "kit car" vs. feeling like an exciting "exotic" car.

One nearly forgotten element of noise reduction is sound insulation on the inside of the engine cover. If the underside of your S1's engine cover has splotches of old, brown-ish colored, dried-up glue all over it, it is likely all that remains of where foam sound insulation once existed. In most cases, the last anyone has seen of such insulation was at least 15-20 years ago, as on most cars it has all crumbled and fallen away since then. Few people have attempted to recreate this insulation in the upkeep and restoration of their cars.

Last week, Patty and I drove 454H over 1200 miles each way down to Orlando, Florida, and back for the Celebration Exotic Car Festival (which was even more fun and exciting than last year's). I had been meaning to install new engine cover sound insulation for some time, and the prospect of covering roughly 2500 miles in less than a week was the perfect impetus to get the job done.

In the past, I had wanted to do it, but had concerns that others have probably considered, too: 1) what kind of material will be able to safely withstand the heat and possible fumes/chemicals of the S1's hot, enclosed engine environment, and 2) how can this material be safely adhered to the underside of the engine cover without risk of it falling or drooping onto the timing belt or exhaust manifold?

I had been keeping my eye out for what might work best, and I finally decided to go with what appeared to me to be a clear all-around winner: Factory hood/bonnet insulation from a Porsche 928. As applied to Porsche's 160+mph flagship, this stuff sits very close to the engine itself, and only inches above the 300+ hp V8's exhaust headers; Porsche are not ones to underengineer or under-specify things, so I figured the material could take the heat and wind for a while in an S1 (especially since it lasts about 15 years on a 928).

And with regard to staying attached against the force of gravity, this Porsche-specified insulation is self-adhesive, and is lined with some of the stickiest stuff known to humanity -- I mean, once it sticks to something, it doesn't come off; you end up tearing the foam off in bits while the layer of adhesive stays glued to the surface. It's amazing, and can obviously withstand the heat, too.

I am aware that supply houses (McMaster, Granger, etc. in the States, for example) sell all kinds of insulation and high-heat contact cements and such; I am more confident in using this Porsche insulation, particularly because I've seen how well it holds up, and have installed it in the past on 928s and 944s.

It is not in the same thickness or texture as the original foam used by Lotus, but this is something I am willing to accept in exchange for what I feel is a safe choice in terms of actual use and performance. The original material used by Lotus is at least 3/4-inch (maybe 1 inch) thick, and smooth, whereas the Porsche material is about 1/2-inch thick and has a waffle pattern to it. Hey, that's cool with me -- the groovy waffle squares are right at home on a 1970s machine!

So, with a great deal of help of my loving, patient wife, we tackled the project of installing the Porsche sound insulation to 454H's engine cover the week before the Celebration show. Below is a step-by-step, with some photos.

After carefully removing the rubber seal from the engine cover, the first, second, third, fourth, and fifth steps were to scrub it clean of 48k miles' worth of grime and grease. It took cleaning it literally 5-6 times with a big jug of purple-colored degreaser, a spray bottle and brushes, to finally get it clean. The first few times we rinsed it, the water was so murky brown that it reminded me of cleaning out the trap of a grill at a fast food restaurant. Special thanks goes to Patty for doing the majority of cleaning here! (while I was busy underneath the car preparing it for the trip) Of course, all work was carried out over a soft surface so as to not scratch the finish on the top of the cover!

Eventually, we knew the engine cover was clean enough when we were able to moisten a paper towel with rubbing alcohol, wipe the inside surface, and not have any color or tint on the towel. It looked like this:

The next step was to make patterns for the sound insulation. I wanted to follow the original as closely as possible. Luckily, Esprit S1 #0134H, the time capsule orange S1 owned by Jeff I. in Florida, has its original foam insulation preserved. Here is a photo I took of it for reference/restoration purposes back when the car was in my possession:

The pieces are obviously cut by hand, as the lines are not even. The cutouts are for the alternator and timing belt areas.

It takes three 928 insulation pads to cover the underside of the S1 engine cover in the same manner. Given that these are espensive (about $90 each) and in limited supply, I wanted to get it right the first time, so I made patterns from paper first. (If I find the source for the 928 pads uncut, I will update this thread.) The patterns were test-fitted together inside the engine cover:

The foam pads were then carefully cut from the patterns:

A center line with end markings was drawn on the engine cover to locate the two main side/top pieces, as seen in the first photo. The actual foam pads were applied from the center line outward, peeling the backing off a few inches at a time. Despite being careful to pat it in place as I went and not stretch or distort it, I wound up stretching it a bit and having to trim it at the edge by the seal.

I trimmed away with a knife just enough of the foam to allow the re-installation of the rubber seal. There were existing blade marks in the cover from when Lotus originally did this at the factory. (And yes, it was quite difficult pulling the little strip of well-adhered foam off...)

Here is the finished product, all shiny and new!

So then came the 2500-mile test drive. On the trip from Toledo to Orlando and back, stopping in the mountains of Tennessee and Georgia, 454H drove through hot southern sun in Florida and Georgia, cool rains, and the cold crisp night of Ohio in April. As I write this, the insulation has held up perfectly -- no hint of peeling off or falling down anywhere, and no hardening or other signs of being affected by the heat.

The change in noise level is dramatic from outside of the car, and obvious from inside the cabin. If you are standing next to the car while idling, you really don't hear the engine at all; the stock exhaust is louder than any noise coming from the body. If you crouch down by the wheel, you hear the engine noise from through the wheel well. But more important is inside the cabin: At most speeds, the interior volume is pleasantly reduced. For the first time, we were able to have a conversation in the S1 at almost a normal level; it's only mildly noisier than a cheap compact car most of the time. A much-welcomed relief from before. A lot of the noise now muffled is the top-end noise and carburetor clatter; the timing belt is still audible (which is cool, IMHO ). The car still booms under wide open throttle, and still has its noisy, gargly zone around 60mph in 5th gear, although it is reduced. For means of a measure, under all conditions, we are now able to enjoy the radio/CD player in the car with the volume a couple to a few notches down from what was customary before. In short, the S1 is still loud, but the noise is noticeably reduced, making for a more pleasant ride.

Although I am not certain here, I think it is reasonable to believe that the added insulation traps more heat. On the initial trip down it seemed that way, but later experimenting (i.e. driving it without the engine cover) did not produce a lower reading on the dashboard gauge or by feel when opening the rear hatch, compared to driving with the cover in place. As I write this, it seems to be fine, but should heat either become a concern or clearly a non-issue, I will update this thread. For now, my belief is that it is warmer under the cover now than without the insulation, but not enough to be considered abnormal or too warm, especially considering that the cars had thicker insulation when new.

To conclude, I am happy with the outcome of this little project. The reduced noise allowed us to enjoy our trip that much more pleasant, and the car still sounds neat, even more than before.

Edited April 26, 2010 by Tony K

[cjtpb13]

Looks like another job well done there Tony...

[peteyg]

Cracking work Tony. I really must try it on the S2. I was only thinking over the last week when I've been doing quite a few motorway miles that, at 'entusiastic' crusing speeds, it's just too loud and uncomfortable, can't hear the radio or the passenger!

Does the stuff have a particular name?

Pete

[Tony K]

Thanks for the kind words, Christopher and Pete.

Pete, I don't know the name or source for the material, but it is part number 928-556-285-02-M260 for a Porsche 928. I'd love to find the big waffle iron batch from which they are cutting the 928 pads and buy some in bulk, or maybe commission a run of Esprit insulation pads.

Do note that I edited the last full paragraph, talking about containing heat. I'd like to do a bit more experimenting (perhaps running with this cover and with 155H's uninsulated cover back to back for comparison, maybe checking with an infrared gun, etc.) to be able to make more conclusive statements about what to expect before others go out and spend their money. I'm happy with it so far, but allow me to be the guinea pig for a little bit longer.

- T

Edited April 26, 2010 by Tony K

[Paul Coleman]

It sounds as though it's worth doing this but at $270 it isn't cheap. Would Dynamat have done the same job and been cheaper? Or would it not stand up to the rather harsh environment?

Cheers, Paul.

Edited April 26, 2010 by Paul Coleman

[Hemlock]

Tony great thread, thanks for sharing.

Good timing as I was actually thinking of possible/different ways to do reduce the noise coming from the engine.

Could you share the cutouts' dimensions for the alternator and timing belt areas ?

Best.

[GavinT]

are you taking orders Tony?

[Tony K]

It sounds as though it's worth doing this but at $270 it isn't cheap. Would Dynamat have done the same job and been cheaper? Or would it not stand up to the rather harsh environment?

Cheers, Paul.

Hi Paul,

I didn't consider Dynamat because I wanted to get reasonably close to original (i.e. foam). But giving it consideration now, here are some questions I'd raise: 1) it's heavier than the foam -- might make the engine cover heavy to lift? 2) In how many separate pieces would it be applied?-- more edges to start peeling off, or do they sell it in big sheets?; and 3) Will Dynamat adhere well to the cover, and will the adhesive withstand the heat? These are some of the considerations I gave to other materials, and why I thought the Porsche stuff would work. Again, I was giving a nod to originality in choosing foam (even though it's not the same), and in making the pieces the same shape; but if you think Dyanamat might do it, give it a shot.

As a lower cost alternative, it might be possible to pull it off with three pads from a Porsche 944, if you don't mind piecing it together with odd shaped/sized pieces. The 944 liners have a bumpy texture instead of a grid, are a bit smaller, and cost significantly less than the 928 piece. 3 944 pads might cover it, 4 definitely would (probably not in the original pattern, though. I decided that I won't miss the extra money spent on three 928 pads, but if I took a shortcut and hodge-podged it together, I'd be looking at it for the life of the time it's on there. I also see an advantage to using only four large pieces per original in that there are fewer edges to start to hang down (not that I think the Porsche stuff will do that).

Tony great thread, thanks for sharing.

Good timing as I was actually thinking of possible/different ways to do reduce the noise coming from the engine.

Could you share the cutouts' dimensions for the alternator and timing belt areas ?

Best.

Hi Hemlock,

I just "eyeballed it" (estimated) from looking at the photograph. The round hole is about 5.5-5.75 inches (sorry, ruler doesn't have cm), and the U-shaped cutout is about 6 inches wide and 7 inches high. I believe I cut them a little bit larger than the originals. I did this intentionally because I knew I wouldn't get them in the exact position, plus my alternator is in a slightly different position due to 454H having air conditioning.

Really, I'm not even sure if the cutouts are necessary or even in the correct location; the thinner material may not interfere. I just cut the pieces out because Lotus had done it, and enlarged them slightly to account for if they might not be in the right place. For what it's worth, after 2500 miles, there are no marks on the foam from anything touching it.

I think that if you just mimic the photo closely, it will be good enough. You might want to sit in the car with the engine cover in place, turn around and look out the bulkhead glass, and note the position of the pulleys while someone lifts/tilts the cover away from the engine.

are you taking orders Tony?

I'd love to find this material in bulk and cut a bunch of them out for everyone . . . .

Edited April 27, 2010 by Tony K

[Fridge]

Hi @Tony K did the S1 engine cover only require material from a single Porsche 928 bonnet (hood) insulation pad?

[Tony K]

Hi David, 

  It took three 928 insulation pads.   As an update, now seven years and about17K miles later, it is holding up well, only slightly damaged where the coolant expansion tank nearly touches it.  

- Tony K

[Freemason]

On 27/04/2010 at 03:55, Paul Coleman said:

Would Dynamat have done the same job and been cheaper? Or would it not stand up to the rather harsh environment?

 

Awesome job Tony!

I'm thinking of doing a similar thing but with Dynamat Hoodliner acoustic foam. It's 3/4" thick, with a cleanable aluminised skin.

[Fridge]

Hi,

I ordered some of that NASI soundproofing from Germany and applied it to the inside of my newly restored S1 engine cover. Looks great and can't wait to test (another 8 months away).

Unfortunately I've hit TLF buffers for uploading photos. Not sure what all that is about. So I've posted them on the Facey B Esprit Group if interested.

@Tony K I sent you a DM from Facey B. Not sure if you realise. Facebook is odd like that.

Thanks for the heads up on this stuff.

[marode]

On 26/04/2010 at 08:53, peteyg said:

I really must try it on the S2.

Pete, now that you´ve had about 10 years to put your S2 sound insulation plan in action, how did you get along?

[peteyg]

@marode

Ha, I've not done a single thing about it!! I guess I've just decided to enjoy the noise whilst I still can and if I want to go somewhere in quiet comfort I'll take the wife's car!

Pete