Does a downpipe make a difference? Part 2
 

So a while back @Lex; made this post:

http://www.mazdaspeedforum.org/forum/foru...erence-126226/

with a link to our blog article:

Blog : Does a downpipe make a difference on a stock turbo MazdaSpeed3? : Stratified Automotive Controls

regarding this subject. It was met with a fair amount of skepticism and even today people discuss the DP as being the big power adding upgrade that everyone needs to do.

Ideally, testing would be conducted on the same car, on the same day, in the same conditions, similarly to the testing that was done in the original iteration of this thread above. There a gutted OEM DP was used which I think some people thought was not a fair comparison to a well designed aftermarket, catless DP. So we didn't have the ability to do this test in an ideal conditions. In fact, aside from me, no one knew a test was even being conducted. I'm sure there will be some debate about the validity of the results, but keep in mind here that the point we are attempting to make is that the gains seen from upgrading the OEM DP on the K04 turbo are not as big as you might be led to believe. For many, including myself, they are not large enough to warrant the expense or work involved until the turbo is being upgraded.

Having said all that, here is what happened. Saturday April 12 2014 was the Epic Nator Meat (ENM) dyno day at Moore Automotive in Fairfax, VA. From the results, I took the four top power producing K04 results, listed their mods and graphed the runs in WinPEP7.

All car owners provided me with the details of their setup on that day; non-power mods and obvious things like AP and HPFP internals have been omitted. All cars were tuned for the mods that were installed during the dyno day with the exception of the TMIC on MZRSPEED's car. The four cars/owners and mods were:

@CWP_MS3;

• 3" SRI +TIP (Ghetto style)
• eBay LONG catless DP
• Ulitmate Racing CBE
• 50/50 E85
• OEM TMIC

@Mike@Stratified;

• SURE Aeros 3" ID intake
• CP-E TMIC
• SURE testpipe
• OEM DP
• OEM CBE
• 25% E85

@MZRSPEED;

• 3.5" SRI
• Stratified 3-port EBCS (assume in 3-port mode?)
• Full catless DP to resonated only exhaust
• 50/50 E85 with Water only injection via D03
• CP-E TMIC (on loan for the day)

@SBMS316;

• JBR 3.5" WP intake
• Cobb FMIC
• J2 eBay long catless DP
• HKS CBE
• 25% E85

http://www.mazdaspeedforum.org/forum/foru...0&d=1398475091

So there you have it. Hopefully this helps some of you looking at upgrades make the decisions that work for you best.

That's crazy, negligible differences. The top two hp vehichles also could have more of an agressive tune.
Moral of the story is, save that money for better suspension lol.

I am happy I have a ebay DP $130.00 wasted vs 600.00+ premium DP:fest30:

All tunes were the tunes the cars drove on every day; no dyno queen tunes from what I've been told.

Sent while Stratified.

Does a downpipe make a difference? Part 2
 

I paid 149.99 shipped for my long, cat less dp. There are plenty of guys who spend that on race pipe alone.

The tune I dyno'd on, was the same tune I drove to and from the meet (2k+ miles) on. And is pretty much my dd map.

It is true that there are a lot of inexpensive options out there for a long catless DP, and the quality of some is pretty good. Adding a cat though, for those of us that have to deal with emissions, adds cost. For me the 8hp difference just wasn't worth the trouble or money. For someone debating about upgrading to a 3-3.5" intake versus a DP, or an upgraded IC versus a DP, I think this will help make decision a bit easier.

Incidentally, whenever I get around to strapping my BNR on the car I plan to see how far I can push the OEM DP and CBE before upgrading as well :)

At what point in the modifications, do I have to have a tune? So far I'm just cat back and cold air intake

C'mon dude, really?

You should really search the forums for your answer. Knowledge is definitely power here. From my brief experience you should look into upgrading your HPFP first, and then worry about a tune (Accessport v2 is what I just bought).

This is a good guide:

Blog : The modification path in a MazdaSpeed/MPS vehicle : Stratified Automotive Controls

I hate to veer off from the point of this thread but this is a question I have been asking myself a lot lately since I am wanting to upgrade my intake and that is, is it worth it to go 3.5in or will 3.0in be just as effective even if I throw a bnr on later? I wish I could see the g/s on these runs

With IATs ~80F and BATs ~100F I was maxing out at 275g/s. With IATs at 55F and BATs at 75F on a street pull I get ~295g/s. If the other guys with the 3.5" intakes had their dyno pulls logged perhaps they can chime in. I do not plan on upgrading the intake when I put the BNR on, at least not right away.

@jdspeed3; made similar numbers on a 93 tuned BNR, but I don't know what his setup is. Maybe he'll chime in here with his intake size and what kind of flow he sees.

Thanks Mike for the data excellent data. IMO, the only downpipe that I have seen make a noticeable difference in HP was the CS which is a totally unique design.

Any logs for these runs? @Mike@Stratified;

I think I can find my logs, but it won't be for a few days. I think they are on my thumb drive at work.

Wow those are good numbers, I wouldn't think the g/s would be affected that much by 25 degree difference in BATs

When I gutted out my OEM dp I only gained like 5 g/s flow. Even when I had the cat in, the difference between mine and a fully bolted speed was negligible. If I had to do it again I'd just keep the OEM dp as is and get other bolt ons and/or meth.

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Setup is fully bolted on a 3' intake, catted DP. I'll post a log of my dyno when I get home.

ive had my car for almost 3 years, and when i finally get my hands on a downpipe, you guys post this kind of shit. i bought mine for the smell anyway.

LOL at buying for the smell. To be fair, we've been saying this exact thing for almost 2 years if you look at the links in the OP.

so from what i'm reading, you should consider a downpipe a 'preparatory' mod for a larger turbo, with small perks in the meantime? i got a killer deal on a CNT, so realistically i'm still happy with my choice.

Pardon my ignorance, but wouldn't the dyno queens show the real differences since you'd be trying to reach the limitations of your hardware?

@Mike@Stratified; thanks for this informative post. My setup is very similar to yours except that I have stock diameter SRI and TIP. Looks like my money would be better spent on a bigger intake than a down pipe, and that is a whole lot easier install. :)

Double tappin' the Moto

The Speed6 had noticeable improvement with full intake and test pipe. I think Mike just saved me from spending almost $600 bucks on CPE's Catted downpipe. Thanks Mike.

Now where would I be better off sending that money.......decisions......decisions.....

Excellent write up Mike! Guys remember that you can't compare the maf g/s from one intake to another since the car does adjust Afrs at wot so the maf cal might not be spot on at wot.

Why has wgdc not been discussed. Sure peak power may be the same but who's pushing their turbo harder.

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Good point, but based on your sig, you must be pushing your turbo really hard :shock:

If only my car was stock making those numbers.

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Higher WGDC doesn't have much to do with pushing the turbo harder.

The speed of the turbo is what generates boost and airflow. Keeping all else the same, you will need the same airflow on all these cars to achieve similar power numbers. So that means that they are spinning their turbos just as fast.

The turbo is spun by the pressure differential across the turbine. That is hot exhaust going from the high pressure in the manifold and flowing through the turbine to the low pressure side in the downpipe.

The wastegate simply regulates that pressure differential and the turbo speed.

If the downpipe has a catalytic converter and is restrictive the wastegate must close more to divert more exhaust though the turbine since the pressure differential is SMALLER between the two sides of the turbine. This means you need a higher wastegate duty.

Once you have a catless setup, the greater pressure differential spins the turbo faster and the wastegate must be opened more to maintain the same turbo speed. So the wastegate duty is less.

However in both of these cases, the turbo speed remains the same.

And in both of these cases the turbo is driven equally hard.

Thanks for the help, some of us on here rant as experienced

Thanks for the help, some of us on here aren't as experienced as others. I don't think any question should be a dumb one. Thanks for the people who pointed me towards the right direction.

Cheers

This..^^^^ Was under impression that the DP was the "biggest bang for buck" upgrade. Very disappointed now, just ordered one from Edge yesterday lol. Now it sounds like I should have ordered new TMIC.
That said..thanks a lot for the detailed information - and for the clarification on the WGDC!

Thanks for the data, dynamic duo at Stratified. I've seen just as great of variances between completely stock MS3s on the same dyno at similar temps.

So I am assume that using a catless set up is more efficient, but if that is so where are the losses associated with a smaller dp across the turbine? Hotter turbine since no gasses are bypassed?restrictions equal heat ie higher get? Am
I to understand that someone making 20 psi with 100 wgdc is not working their engine harder than some one making 20 psi with a wgdc of 30? Maybe the correct wording would be stress on components. Maybe the stresses are very small bit it could be the difference between a 80k k04 and a120k turbo.

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I've been daily driving this map 50 miles a day for almost a year and a half, with only a 3 week period of 93 octane, while I was fixing my fuel level sensor.

Bolting parts on without a tune is like throwing money away. It changes your sound, but without a tune its adding little to no benefit. If anything, money should be spent on a tune first, if you goal is to go fast.

The whole point that Mike was making here was that you could practically go for a 100-200 intake and tip, coupled with a tune, and end up with a 320+ whp car.

I can flow up to 300g/s on the street. I'm not sure what it was for this dyno day because I didn't have them take logs. My 3inch is only the maf housing itself, and funnels down to a normal sized TIP.

If anything a catless downpipe allows you to run more boost and therefore spin the turbo faster thus working the turbo "harder".

The reason a more open exhaust makes more power stems from the ability to run more boost and to have lower pumping losses.

As it turns out the large modern catalytic converters flow well, the k04 can't be spun much faster regardless, and the majority of the pumping losses come from the small turbo hotside and turbine. Flow depends on the cross sectional area as well as the density of the cat and the oem one although dense has a large cross sectional area (diameter) compared to aftermarket ones.

This is the same story on the Focus ST where a downpipe makes even less of a difference.

Meh....

I like knowing I'm getting everything I can out of the k04, even if it is only 5-8whp.

Besides our platform is performance oriented that being said 80% of the community will eventually end up going BT, it's just one more thing checked off that BT list.

80% go big turbo? more like 5%...

Lol!

80% was slightly exaggerated

I've been telling people and posting that link in numerous threads in the last couple of years. People just don't want to believe it - hell, in the NorCal thread the recent discussion has been "Mah GAWD! Just put a DP in and the POWAH!". lol

Anyhow, thanks for the additional info and maybe continued exposure to this kind of data will finally allow the truth settle in. :wink:

It's nice to see some actual numbers to back up my own mod path decisions. I am in progress on a Stratified tune right now with an intake, TMIC, and test pipe. I had decided that the downpipe was not worth the money and headache. This thread has just helped me be even more sure that I made the right choice.

Double tappin' the Moto