Delorean Performance Industries Spec 1 Stainless Steel Exhaust

I thought I would wait until a few months of use to review this exhaust.

Who else has this exhaust?

It has met my expectations. I have not heard any exhaust leaks/ticking over the past couple thousand miles that I have used it. Thank you very much Josh Bengston for making this available!

The installation fitment was excellent becaust DPI test fits each exhaust before installing, so I had no problem once I put it on my car. However, be fore-warned that you have to clean out all of the cylinder head exhaust stud threads very well as this exhaust takes advantage of all 4 per cylinder. This took me a lot of time to complete. You may also want to use lock-tite or lock washers to keep the studs and nuts from backing out or coming off of the headers; I know from experience.
The headers were designed well so that you can easily tighten all of the nuts down with a wrench or socket. You want to put everything together loose before tightening; the muffler brackets, converter pipes, headers, etc. It's a slight pain at first but it all fits together well. Also, you have to reuse the original bracket "doughnuts" that bolt to the exhaust brackets and that the hangers from the exhaust slide into. I experienced some necessary persuasion on getting the doughnuts off and on the original and new exhaust hangers....

One other thing that I would add is that you need to make sure the heat shield on the muffler is tight and perhaps use lock washers or lock-tite. Otherwise the bolts will back out and you will have an annoying vibration; again, I know from experience. Also, by having the bolts tight, the shield will bow a bit because it can't expand/contract with the exhaust heat of the muffler. Perhaps slotting the holes will allow it to adjust to the hot/cold temperatures; but it's nothing major to worry about.
The exhaust note is very deep at idle and low reving rpms. The interior resonance is minimal when cruising on the highway, which is a plus for me.

There are two welded bungs, one each on the headers. The stock oxygen sensor requires pulling the wire out of the firewall some, but it will still work. You can add an extension if you wish. The otherside is handy for using a wide-band sensor or tuning; a nice option to have available.

Performance-wise I definately noticed a difference going from the stock exhaust to the Spec One exhaust, especially when I have the upgraded DMC CA cams and did port/polish work to the cylinder heads.

Also, my stock exhaust had a cat-delete pipe. My wife and I would notice that the garage would smell like gas after turning off the car and closing the garage door. With the Spec One exhaust, that smell is no longer noticed. The catalytic converters do not hinder performance and also absorb the fuel smell instead of your clothes, hair, and eyes...plus they are smog-friendly for those who need it.

Overall this is a great product; high quality, excellent fitment, good looks with a nice clean/tight/tucked design, excellent sound, and great performance.

Josh Q

Pictures below:
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I have this exhaust, very nice throaty sound at low RPMs but smooth and quiet at highway speeds. Very nice fit and finish.
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I like the look for sure but Wilson's looks shinier. Is this a camera trick or is he selling two different finishes?

He has the ceramic coated version that costs more.
I made an economical decision and ordered mine plain stainless steel.
His exhaust and car are really nice looking!

<blush>
Realize I had an entire engine refurb done at DPI with the appearance option. It sure didn't look like that when it was towed in there...

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Originally Posted by DeloreanJoshQ

He has the ceramic coated version that costs more.
I made an economical decision and ordered mine plain stainless steel.
His exhaust and car are really nice looking!

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One thing I noticed about this exhaust visually is that the exhaust pipes seem to be real short and just barely make it past the bumper. It sounds real nice but seems louder to me in the cabin area to me than what I am used to. Im running the UK SS set up so I am used to that sound. Other than that it seemed to be a nice set up.

Glad to see so much positive feed back on this system. Just to take out the confusion on the issue our systems are exclusively produced for DPI to our specifications by Stainless Works here in Ohio.
We sold a number of used Houston Stage I systems recently and owners are under the impression these were also produced by SW. This is not the case. As far as I know Stage I kits are produced in Lancaster CA by Thermal Research and Development. Our systems have nothing in common other then the fact that they are dual in dual out. Parts are not interchangeable either.

I too have been very happy with mine. However, to correct the OP, you only need two studs per exhaust port. Nothing wrong with doing all 4, but the standard kit only comes with two studs per port. In my case, I left the original studs in place as I didn't want to deal with them and used the unused locations for the new studs. It's not as nice looking with the old studs still there, but most won't notice.

As for the heat shield bolts, I've lost about 6 of them on the road as they backed out. The current ones I have in there now have both lock washers and thread lock. So far so good! But that's been my only issue with this system. Otherwise it's been fantastic and I highly recommend it as well!

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Originally Posted by Chris4099

I too have been very happy with mine. However, to correct the OP, you only need two studs per exhaust port. Nothing wrong with doing all 4, but the standard kit only comes with two studs per port. In my case, I left the original studs in place as I didn't want to deal with them and used the unused locations for the new studs. It's not as nice looking with the old studs still there, but most won't notice.

As for the heat shield bolts, I've lost about 6 of them on the road as they backed out. The current ones I have in there now have both lock washers and thread lock. So far so good! But that's been my only issue with this system. Otherwise it's been fantastic and I highly recommend it as well!

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Mine did the exact same thing. One of my heatshield mounts actually snapped off due to the vibration and the bolts being locked in place. I have the car in the shop right now and Josh is gonna fix the problem so I'm happy.

The problem we have found with the hardware coming out is mainly due to it not being checked post install. Most times the shield is only installed finger tight by SW when manufactured. Unfortunately owners think it is fully installed. Hardware falls out and then is reinstalled after the shield has bedded in after a heat cycle. This can cause extra stress on the welded z brackets and cause a break to occur. We are now supplying a check list with the system of fasteners to check during install prior to starting.

I've added lock washers on my bolts as well after losing a few. The heat shield is warped as expected from the heating/cooling - should I remove the lock washers now that the shield is set? I'd hate to have a bracket break...

Yes the shield needs to be able to deflect under different heat loads. The lock washers will force it to bind on the slots.

Thanks for the fast reply, I'll remove them before any damage is done!

Its actually not the lock washer but the orientation of it. If it is installed where the cut on the washer can bind in the shield hole there will be a problem. If you want to use a concave tension washer this is safe to do as long as there isn't a serration pattern stamped. We install just the 1/4 -20 bolts and use the machined underside of the head for seating on the z bracket. This give the proper tension.

Thought I would lend my two cents here. I installed the DPI exhaust and I am very pleased. I agonized for while before choosing this. The other venders may be excellent also, but I assure you will be happy with this. Of course, mine is their newest version. I guess they made a few changes based on customer responses. I can't say I would change anything on mine.

-They look fantastic
-They fit perfect
-They do add some power (don't expect miracles)
-The sound is ideal for me

I will expand on the sound. It is slightly louder and more defined when idling or winding through the gears. But when you get to 60-80 cruising speed, it settles down to a nice background tone. It also makes a nice "burble" sound when you let off the throttle quickly. I have made a 700 mile trip (one way) and I'm completely happy with this exhaust.

Of note, the tips are the most polished SS I have ever seen. I kind of prefer a brushed look there, but could not convince myself to scotch brite that beautiful finish. Lol.

I have an update to this thread. One of my concerns with headers was how easy can you change the starter and alternator. I carry a spare of both on trips because nobody stocks them. (Auto parts stores)

The alternator is easy to change, even without jacking up the car. Today, I confirmed I can change the starter with the small tool box I carry in the car. It does require jacking up the car and you definitely need to wait for the exhaust to cool.

I would recommend putting a insulated wrap on the starter and muffler. When I received my car the starter already had one. A couple years ago I put one on the muffler and I'm glad I did. It keeps a lot of that heat out of the engine bay! It definitely makes opening the engine bay on a warm day at a car show more bearable.
I also have headers and I don't think wrapping them is really necessary.


Dave B.

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Originally Posted by WHO1DMC

I would recommend putting a insulated wrap on the starter and muffler. When I received my car the starter already had one. A couple years ago I put one on the muffler and I'm glad I did. It keeps a lot of that heat out of the engine bay! It definitely makes opening the engine bay on a warm day at a car show more bearable.
I also have headers and I don't think wrapping them is really necessary.


Dave B.

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Funny you mention that. I installed a remanufacture “Premiere” starter before the headers a few months ago. It still worked, but it was “ticking” lately. (Like the solenoid was not quite working.) I’m not sure if heat played a part in its early demise. If this new one starts doing it, I will wrap it with some kind of insulation. I bought two “lifetime” starters at Autozone. The guy at the zone couldn’t understand why I would buy two when they are warranted for life. (I did the same with the alternator) The zones parts quality is really lacking, but their lifetime service makes up for it.

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Originally Posted by Helirich

Funny you mention that. I installed a remanufacture “Premiere” starter before the headers a few months ago. It still worked, but it was “ticking” lately. (Like the solenoid was not quite working.) I’m not sure if heat played a part in its early demise. If this new one starts doing it, I will wrap it with some kind of insulation. I bought two “lifetime” starters at Autozone. The guy at the zone couldn’t understand why I would buy two when they are warranted for life. (I did the same with the alternator) The zones parts quality is really lacking, but their lifetime service makes up for it.

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My original starter is still doing well "knock on wood". But I have a premier incase it decides to puke.



Dave B.

Anybody in the New England area with this exhaust system?
I’d like to hear it in person before pulling the trigger.