To wrap the DP or not to wrap the DP?
 

Hey all,

I'm getting ready to install my downpipe this weekend, and I was wondering who has wrapped, who has not wrapped, and what harm could come from wrapping or not wrapping your DP.

Thanks in advance!

i did it, it killed the high pitch whine of the turbos, i hated that

i havent wrapped mine yet but im sure its helps with heat no doubt, just wrap it. wrap it up baby!:D

really? thats weird, my friends turbos(who has a wrapped dp") were crazy loud, and i thought it was from the wrapped dp. maybe it depends on the dp?

it's better not to wrap i guess..(juz my.02) it helps coolin the exhaust durin hi speed..

Noise doesn't kill a rotary engine - heat does.

Are you more concerned with how the turbos sound or how long the engine will last?

Be smart here.

I didn't wrap mine, but if given the choice again, I'd definitely wrap it.

Wrong.

We're not interested in cooling the exhaust, we're interested in making sure the exhaust does it job correctly - move exhaust gas out of the car with minimal flow disruption and heat transfer to the rest of the car and in addition aid in scavaging any unsed air/fuel past the exhaust ports.

Well I wrapped the down pipe on my T2. If you wrap your downpipe you will reduce underhood temperatures(not sure how significant of a change), keep the heat energy in the exhaust which will means higher exhaust velocity=less backpressure=more power reduced turbo lag.. (again not sure how significant)
Err.. disadvantage is that people have reported a reduced lifespan of wrapped downpipes, If your dp is stainless steel you don't have to worry about rust... if it's cracks in the welds... don't worry about it, it would probably still last up to 5 years.

true enough, but to me i just like the sound :D

and anyways, my engine didn't last very well at all and my downpipe was wrapped :)

Great replies so far, thanks guys!

Is there any absolute disadvantage to not wrapping (besides the possible slight performance difference)? Specifically, doesn't just adding a DP in and of itself reduce underhood temps by a good 100 degrees? Is there that much more of an additional reduction in heat by wrapping it?

I have an M2 downpipe that I'm installing if it helps (as far as durability goes). I suppose if I decide to wrap it I can just get the materials at a local auto store?

Thanks again!

yea man it corrodes a bit faster, but it does drop temps quite a bit, If it didnt serious racecars and things of that nature wouldnt use it, Its there for a purpose.

-Chris

the place where our dp mounted has potential of air to metal coolin..coolin the dp exhasut(exhasut=heat) is similar concept of wrappin the dp (removin heat) that's what i was thinkin.. but i will choose to wrap the part near the turbo and let the bare metal out coolin where itz sat near the transmision area

Well.. If you wrap it up with 2 layers or just even 1 you can touch the dp without getting burnt.... well.. for a good while that is.. but I don't recommend you do that.

If it were up to me I'd wrap the whole exhaust system from turbo all the way to the exhaust pipe.

As far as cooling goes you only want to reduce underhood temperatures and for the exhaust gasses tuners try to keep the heat energy in it so that exhaust gas velocity will be maximized.

:) u guyz literaly convincin me to wrap that bitch now.. thats why i stay this forum much more the other. u learn every day.. Thanks

Wrap the entire car. Leave the windshield unwrapped so you can still see out. ;)

I wrapped on a small section of my manifold(Single turbo) and my exhaust temps went up over 100C!!!

I'd rather have high underhood temps than have 1000C EGTs:)

Well... if you feel that way... Then you'd rather have higher intake temperatures. and an overall hotter running car.

It doesn't matter really.... if you place your exhaust temperature probe exactly where the exhaust gasses are being expelled from the engine it shouldn't make much of a difference in reading....

Besides exhaust gas temperature readings is only a way to detect fluctuations in A/F ratios and does not really tell you the whole story.... you'd need a wideband for that... I don't have much experience.... well no experience in A/F tuning but I will bet my lunch that you can have similar A/F ratios at different temperatures.

Hotter intake temps can be combatted by having a good FMIC and/or water injection.

My EGT location didn't change....the only thing I did was go from no heatwrap to heatwrap in ONE little itty bitty area because I had an oil return line near the manifold, so I wrapped the manifold to keep the heat from getting to the hose. Prior to this, I would see 920c~ in 4th gear, 9000 rpms. After I heatwrapped, I saw over 1000c in 4th gear, 9000 rpms.

According to my wideband, the a/f are exactly the same as before. HOWEVER...hotter EGTs = bad for engine.

Why?

From my experience a wrapped DP will rust much quicker than an unwrapped DP. I'd get it HPC extreme coated instead.

I agree with that.

If you got the $ go for this: http://www.jet-hot.com/

yeah, but who cares if it rusts? it is only surface rust and will take many, many years to rust through to the point where it needs to be replaced.

Lets make one thing perfectly clear:
- You wrap a downpipe to decrease temps in the engine bay.

Read up on how many posts point to excessive heat causing FD engine failures as well as failure of other related parts such as fuel hoses, the rats nest, brittle vacuum hoses, etc. Fuck it if the downpipe rusts. Its only surface rust and if it does happen to rust all the way through 10 years from now, its a $200 part vs. everything else.

By keeping heat inside the downpipe instead of radiating out onto all the other parts in the engine bay. If jspecracer realized a 100 degree increase in exhaust gases in the downpipe, then that is at least 100 extra degrees cooler underhood.

Thanks dude! I really laughed my ass off to this one! Cooling the exhaust... :weed:

Thanks for the replies, guys.

Are you saying that you won't reduce engine bay temps if you don't wrap it? I thought that you do some serious temp reduction just by installing a DP to begin with...

I think he means that it will reduce engine bay temps even more with a wrapped dp

That temperature differential upwards you saw is a result of that SAME heat not being radiated into the engine bay.

High EGTs are bad if the engine is creating those same EGTs without wrapping - not because it is successfully moving more heat out.

Keep in mind that exhaust wrap costs ~$100 for 2 ft's worth of piping :eek:

*priced @ SuperAutoBacs in SoCal, so it might be a bit cheaper elsewhere :(

I got mine from summitracing.com paid $36 and it was enough to do the whole exhaust system.

http://store.summitracing.com/partde...rt=THE%2D11002

err,.... well shipping is free from summit but the charge a handling fee of $6 so it came up to $42

Haha. Gotta love Summit.

I always laugh my ass off when I see the prices at these import-specific places and then compare them to the prices at Summit for a similar part.

People are getting taken so hard.

yeah man... summit is da bomb :D...
gotta love that salese gimmick though.... free shipping pffftt.. who are they foolin.
:mad:

How about $35 for 50 feet of 2 inch wide wrap at Summit:
http://store.summitracing.com/defaul...-Tec&x=10&y=13

Thats funny... in the time it took me to find the sight it was already posted!

I beat you to that link :D

I would haft to say that Jet Hot is some fantastic stuff for intake, exhaust, and turbo housing's and if you are the type of dude that likes to get the best out there, and have some extra cash, try it.

Yeah, I'd like to try that on some of the parts you mentioned. the downtime for shipping back and forth sucks though...

A good coating (HPC, Jet Hot, etc) will contain the heat MUCH better than a wrap.

And a rusted DP looks like ass if you ask me.

Well... if get a stainless steel dp it shouldn't rust. and yeah I guess a good coating is better than wrapping.. my friend had his dp on his subaru coated and you touch it and not get burnt even after a hard run..

Some of this was partially addressed by others, I thought it might be a good idea to clarify it a little more.

You're measuring EGT as an indicator of AF in the combustion chamber. The hotter it gets the leaner the mixture within normal ranges. If you saw an increase in EGT from thermal wrapping a pipe it has nothing to do with the actual mixture in the combustion chamber, which is what you care about. When you saw that increase in measured EGT it didn't change anything with your internal combustion ratio. Your new measure of 1000c is the exact same running conditions as when it read 900c without the thermal wrap. So if you used to tune for 900c now you'll instead tune for 1000c. That really should be very common sense but just in case.

Others also mentioned the issue with header wrap causing longevity issues. Yes it does. It's usually very acceptable though. When the exhaust and wrap cool down after the car is turned off moisture will condense on the exhaust and wrap and act a little like a wet towel around the exhaust which is where the rusting comes from. The other side is that the pipe will experience more thermal fatigue being exposed to on average higher sustained temperatures and times since very little heat is radiated away from the metal surface after being wrapped. This means in sections that support weight etc. you'll see fatigue cracking much faster than normal and thinning of walls on the outsides of bends etc. It's still very worthwhile though in my opinion, the reduction in life is usually beyond the scope of how long most people will own their cars. I use it myself but only on Inconel and stainless tubing.

Kevin T. Wyum

If you re-read my post, I STATE that the a/f did not change...only the EGT's.

FWIW, One of my motors had atkins apex seals in it, which do not like high EGTs. I had my car tuned/running/racing for four months with this the same setup during the summer. I beat the crap out of the motor time and again every sunday(our race day). I put on exhaust wrap on that small portion of my manifold...EGT's shot up to 1000 C+....2 weeks later, my motor blew. I had a burnt corner of an apex seal, where the apex seal and the assist piece meets....my apex seals sure as hell didn't like higher EGTs...but they held up just fine for four months at 920C~:confused:

Yeah, what Kevin says! ;-)

And to prove it, I've wrapped my HPC's "HiPerCoat Extreme" coated SS downpipe. Only about 1500 miles on the new setup, but so far there is not a glimmer of doubt as to the thermal efficiencies of the setup.

BTW, Kevin, who's machining/fabricating all of the Inconel stuff for ya? I've got a couple of ideas I'd like to R&D.

Any preference or known differences between "Thermo-Tec" and "DEI" wraps? Both are asbestos-free and rated to 2000 degrees. Not much difference in price.

http://www.thermotec.com/products/full/11001/11001.html

http://www.designengineering.com/exhaust_wrap.html

Wave to Carlos. Long time : ). Surprised you aren't on the other side of the planet right now. As for the inconel there really wasn't any machining work needed since it was just a matter of cutting bending and welding. It is a complete bitch to work with though. It broke part of the bending machine and my vendor wasn't happy about it. It's pretty ideal material for the header portion prior to the turbo though. Much better than stainless. What ideas do you have? It's expensive to work with whatever they are : ).


For Jspecracer. You've got some really odd ideas about a causal link between your engine failure and headerwrap. I think maybe trying to shift at 9500rpm might have a little more to do with it. Trust me header wrap is not changing your internal combustion temperature like you seem to think it is. Maybe a degree or two in some exteme twist of the header material retaining the heat and conducting it back to the block and through the block into the chamber. (long shot)


Kevin T. Wyum

Well, I am running a T-45S...the turbo keeps making power past the "stock" redline...power drops off at right around 9000~. The shop next to mine has a T-51S bridgeported motor boosting 1.5~ that revs to 12000~ for over a year and a half...trust me, my measily 9500 rpms isn't hurting anything. Besides, a Burnt corner of an apex seal can in NO WAY be associated with shifting too high. Burnt corners(esp. on Atkins seals) are ALWAYS associated with high EGTs, either from running too lean, too rich, or timing being too advanced.:)

Do NOT!! rev to 9500 man. Seriously. Not without the proper bearing and engine setup.

I had my entire exhaust system HPC Extreme Coated(Manifold, Turbo Backhousing, DP, MP, Rear Exhaust section) because I wanted to keep the underhood heat to a minimum, and because the exhaust I have isn't made out of stainless steel so I wanted to keep it from rusting. So far the heat retention has been better than what it was stock, BUT it will still need to be wrapped because I noticed that the wrapping only actually contained the heat better on my last FD(which had the exhaust system wrapped with Thermo Tec exhaust wrapping)than the HPC Extreme Coating I have on my FD now. The HPC Extreme Coating should let me wrap the exhaust system without any fear of rust though, which is one of the advantages I see to it now. So basically what I'm trying to say is that the exhaust wrapping in my opinion retains the exhaust better than the HPC Extreme Coating from what I have observed on my car.

Kevin is 100% correct about everything he has said. I have my system wrapped all the way to my resonated mid pipe. I have had it with and without wrap on different turbos, and both times the performance increased when wrapping the exhaust.

My first setup was with my stock twins. When I first put the down pipe in, I forgot to get the wrap and was impatient so I installed it naked. I drove like this for a while and was very accustomed to how it performed. One day I got a wild hair up my a$$ and decided to pull the downpipe and wrap it. I immediately noticed an increase in power and a decrease in turbo lag. The turbos spool faster with more heat/energy in the exhaust. This is the key, heat =energy which increases flow which is the same effect as putting a better/less restrictive exhaust on in the first place.

One other nice thing about wrap, is that it gets rid of some of the tinny sound you get from going with a stainless downpipe. It sounds much deeper and smoother.

I had my stock twins upgraded 2 years later and had the downpipe out. I decided to rewrap it with my leftover wrap(you can wrap a downpipe 2x with 50 ft of 2" wide header wrap). It looked ugly but was in great shape(stainless). After running like this for another year, I got my apex rx6b kit. I installed it with out wrap, as I was out, and drove like this for a month. I pulled the downpipe and wrapped it and once again the same effect; more power, better spool, and quiter exhaust sound at the engine.

It also helps with under hood temps. As for the increased EGT's this is indicative of the more heat being retained in the exhaust but has nothing to do with how the car is running as it is post combustion. Nothing is changing but a number on a dial after the exhaust has left the engine. All this means is that your new baseline # is higher. I would worry if the # changed from fuel or timing changes and/or intake temp changes, but not from wrapping.

I really do not see any disadvantage from wrapping unless you are using mild steel which has not been coated

mike

Jspecracer....

Where did you put your EGT probe? I've said in an earlier post that if you can place the EGT exactly in the combustion chamber(which is impossible) you will not see a significant temperature differential when you wrap the DP.
In fact if wrapping the DP has a large enough effect on engine bay temperatures, the intake charge temperature should drop and cause the combustion temperatures to drop too.

I'm not quite sure you understand what is happening here. Your exhaust gas temps are not rising from the exhaust ports, they are exactly the same. The position of you EGT probe is likely to be after the wrap, hence you see an increase. If you put the probe before the wrap you wouldn't have seen the rise in EGT's.

The fact your motor blew after installing the wrap is in my unprofessional, but logical opinion, coincidence.