Deleting precats and fitting Wagner IC's --> big gain on stock ECU mapping

[JCviggen]

I was at MRC a few weeks ago to get my car mapped, mostly to get rid of that pesky CEL due to the precats being gone.

The biggest surprise was that the car made 515 bhp (crank) the first pull on a stock map. Few raised eyebrows about that, Mihnea thought at first there was too much coastdown drag in the driveline but that turned out not to be the case. It was genuinly putting out 65bhp more on the stock map (there's probably a margin of error here of 10 to 20hp but even so)

Here's a comparison of my car vs a completely stock car with full cats and stock IC's (mine is the black one obviously...)

http://www.greenringer.net/various/mrc/compare.jpg

515bhp vs 444 bhp of the completely stock car (not unlikely to have some leaks in the ICs) and a much smoother curve. The main difference is at the very top end. The power curve looks more NA with max power at the very top end. Performance once mapped is much better mostly because it makes so much more power in the 4-5.5K range than the stock map. Mapped it did 546bhp with some potential left in the turbos. 441 peak measured at the wheels, but its a double roller braked dyno so it has much higher tire losses than a dynojet would have FWIW.

Vid of the sound right after the precat delete and supersprint exhaust

http://www.youtube.com/watch?v=gj7tbkb-Ebc&hd=1
Autobahn stuff, had to let off at 180mph for roadworks :( It felt like it had 200 in it.

http://www.youtube.com/watch?v=SgBpgoIWUtM&hd=1

11485

[Elevens]

Congrats on the numbers JC. I don't have hard numbers since I have never Dynoed but seat of the pants tells me that after I went Catless (Full Milltek no cats at all) Top end performance Improvement was very noticeable. I had one last encounter with a couple of big Crotch rockets( big Bikes) just before she went into the shop for a Gearbox rebuild and believe it or not they couldn't touch me. After attaining ridiculous speeds I had to back off due to safety concerns. But top end power was nothing short of amazing. Reducing the restriction behind those turbo's definitely results in a major performance gain......

[kilian tuning]

Nice footage Jan, be careful showing license plates and homes because crazy people are watching these forums too...and the RS6 cars are on wanted lists...even without keys...

[JCviggen]

Not worried about that m8, the car is registered to an address on the other side of the city ;)

[kilian tuning]

Still happy with the FK Koni coilovers?

[JCviggen]

Yep car has setteled very nicely, marginally more comfortable than my DRC was in the end. Decent handling, not the greatest in the world but I've got them set very soft and comfort was my first concern. It's definitely not worse than DRC in any way though.

[hahnmgh63]

Congrats on the numbers, nice improvements. I'm looking forward to re-installing my engine w/ gutted pre-cats and fresh rebuilt Turbos & tranny/T.C.

[kismetcapitan]

as a rule of thumb, I've never built a turbo engine with any restrictions after the turbos. IMHO turbos don't like backpressure, period - resonators are ok but nothing where the exhaust flow has to go through chambers. Anything that introduces backpressure is a compromise. Since I always install widebands...backpressure also throws off wideband readings; at best, they're slower, at worse, they read richer than what's happening. Downside is drone, flames shooting out the tailpipe, and loudness. Although the latter two are good in my book :)

Which leads to the question: if you do an ECU reflash that's mapped for straight pipes right off the turbos, what kind of power are people making?? And how about the airboxes...has anyone done cold air intakes with cone filters?

[hahnmgh63]

Yea it is well known that Turbo engines due better with low back pressure. The Turbo's give the engine all the back pressure it needs. Low back pressure aft of the Turbo's helps the Turbo's spool up faster reducing Turbo lag so you get boost earlier in the RPM range and full boost earlier. Potential max boost ends up being a little higher too.

[4everRS]

What are you figuring for drivetrain loss?

[JSRS6]

25-28%...?

[JCviggen]

What are you figuring for drivetrain loss?


25-28%...?

It's never a simple percentage guys. Driveline loss is for the most part rolling resistance of the tires at high speed, the higher speed you get up to the more you lose so it's a rising curve. With double rollers (2 contact patches, more friction than the real road) peak coastdown loss was in the 105-125hp area varying slightly one run to the next (warmer tires made for higher losses) This is probably twice what you'd have on a dynojet. Also important to note is that the losses do not really change as power goes up. So the more power you're making the lower the losses will be percentage wise. And while it may have had 125hp loss at 140mph tire speed, it would be down to 80hp or so by the time it gets down to 100mph so every point in the rev band has a different loss.
So it's best to avoid talking about loss % altogether! Dyno's are tuning tools anyway and results cannot be compared unless done on the exact same one the same day.

http://www.greenringer.net/various/mrc/RSdyno.JPG

The dropoff at high rpm does not occur like that in road conditions btw...caused by intake temps on the dyno, little fans can't simulate 130+mph of airflow sadly.

[micdee]

Very nice figures indeed.
My worry about removing the first cats is my yearly MOT. What does the removal has for a result on the exhaust measurement. Will I still be able to get the needed numbers for CO2 and Nox, I think it is.

[JCviggen]

Very nice figures indeed.
My worry about removing the first cats is my yearly MOT. What does the removal has for a result on the exhaust measurement. Will I still be able to get the needed numbers for CO2 and Nox, I think it is.

Don't need to worry about that. The main cats if left in place will make the car pass no problem. The pre-cats biggest job is to work very shortly after a cold start, before the main cats have enough heat in them. Thats why they located the buggers right after the turbos.
Once warmed up you do not need the precats really.

[kismetcapitan]

It's never a simple percentage guys. Driveline loss is for the most part rolling resistance of the tires at high speed, the higher speed you get up to the more you lose so it's a rising curve. With double rollers (2 contact patches, more friction than the real road) peak coastdown loss was in the 105-125hp area varying slightly one run to the next (warmer tires made for higher losses) This is probably twice what you'd have on a dynojet. Also important to note is that the losses do not really change as power goes up. So the more power you're making the lower the losses will be percentage wise. And while it may have had 125hp loss at 140mph tire speed, it would be down to 80hp or so by the time it gets down to 100mph so every point in the rev band has a different loss.
So it's best to avoid talking about loss % altogether! Dyno's are tuning tools anyway and results cannot be compared unless done on the exact same one the same day.

couldn't agree more that they are tools for baseline mapping and not an accurate power measuring device, and with AWD cars it becomes even more of a guessing game as to what you're making at the crank. If anything, wheel horsepower is as quotable as you can get. Whenever anyone says their car is making so-and-so at the crank, I always take that as a guesstimate, nothing more...unless they dynoed the engine out of the car on a bench.

[JCviggen]

with AWD cars it becomes even more of a guessing game as to what you're making at the crank

Definitely can't compare it straight to RWD numbers because with AWD you are measuring the inertia of 4 wheels rather than 2. But on the road both cars need to get 4 wheels turning. So if you'd have an identical car otherwise an X awhp car would be slightly quicker than X rwhp car...that said, inertia and rolling resistance can be measured fairly reliably on a dyno.


If anything, wheel horsepower is as quotable as you can get. Whenever anyone says their car is making so-and-so at the crank, I always take that as a guesstimate, nothing more...unless they dynoed the engine out of the car on a bench.

Actually all things considered BHP numbers including coastdown losses can be more accurate than pure wheel numbers. Wheel numbers are extremely influenced by the speed of the tires (so the gear you're in basically) and depending on dyno type you can see swings of 100hp at the wheels...the engine's actual output is more constant than what you could measure at the wheels. But anyway...comparing numbers says nothing dyno to dyno...to compare performance you're better off with a dragstrip and see who gets the highest trap speed.

[ttboost]

Interesting conversation....I always dyno my cars on the same dyno...for obvious baseline reasons. Again, like most I realize that the number means squat, but the delta is the important thing. I also try to dyno in the same weather conditions after mods. My car made 318 on a Mustang dyno, stock, back in te 60degree weather. I unfortunately couldn't get back there until recently, when it was 90degrees in the shop. It made 408awhp that day after a flash. So MY car on THIS dyno has a 29% loss, ASSUMING the factory 450crank hp is correct? Probably a little less loss considering the weather. My tuner always dyno's in 3rd as he can't make enough "wind" for a full 4th gear pull. 3rd is even pushing it. We DID however do an experiment with my 996 Turbo on the dyno and made pretty much the same power (the same day and time) in 3rd AND 4th. As I recall it made maybe 3 more whp in 4th (it is a manual).

[JCviggen]

There's always a ton of variables so it's hard to give a one size fits all answer. IF the car made 450 at the crank the first time around (not quite a certainty) that means a total loss to tires and whatnot of 132 horsepower. Add 132 horsepower to your 408 figure and you end up with 541 at the crank. But here's the catch, if you make peak power at a different rpm/speed point you have different loss as a result. If you look at my curves before and after, you see that before mapping it made peak power at ~5800. After mapping peak power was at 5300. The "loss" stock was 126hp, mapped 105. That means basically that the peak wheel horsepower number is much higher. Stock RS6 did 340, mine 375 or so, and after mapping 441. That's a gain of 66hp at the wheels...but at the flywheel the car only made 24 horsepower more as a peak maximum. Funny old game isn't it :D
Basically if you boost the crap out of the engine at low revs you could make peak power at 4600 or so and get a huge whp number (i've seen it on here somewhere a while ago) but in that scenario you're dealing with a very low driveline loss situation which means your engine isn't producing all that much. In your case I suspect stock you made power at high revs and mapped at lower revs, which explains the huge difference in whp. Probably you gained 50-60 max at the engine even though your peak whp shot up nearly 100. Assuming your car is otherwise fairly standard outside of mapping they don't really do more than 500 crank on the stock IC's and full cats.

Turbo cars love high load and need it to make max power...that's why 3rd/4th is usually similar on a manual car. If you try it in 5th thats when you start to see less at the wheels at least, the engine output is still about the same if cooling is sufficient.