FAQ- B6 B7 Exhaust information build Thread

DIY/TECH/INFORMATIVE
#61

yeah, he held it on the hold RPM (5500 or so) for too long, and when you do that for whatever reason it launches weakly.

Want to get to that hold, then go in half a second, not 2-3 seconds.

Here are a few good launches highlighting JHM launch assist

good outside view. Held it for a full second here but still launched well.
http://www.youtube.com/watch?v=aoAxXcM2nN8

speedo/tacho view
http://www.youtube.com/watch?v=vgo9CiIZoZc

speedo/tacho view. Guess the 0-60 time (as measured by my GTECH PRO RR)
http://www.youtube.com/watch?v=AxMkC7F4SyI

this one is me in my car (in car) vs. bangoman in his car in the right lane. I waited for him to start, so I could film him. Couldn’t catch him after giving him a 2.5 second head start unfortunately.
http://www.youtube.com/watch?v=dL94O7iObDQ

#62

Yea but as discussed on the B8 S4 and as Beem has said on the F.I. apps of the B6/7, the blower is going to push through any resistance, part of the reason the crossover in catback isn’t AS crucial (also due to firing order). Making that resistance less is certainly a good thing, but the % gain probably isn’t as great as seen with the N/A guys. I’m not ditching mine anytime soon, I’d just like a good explanation from count or beem etc on the principals of it with the blower other than it’s less restrictive/less boost/etc.

I think you’d be hard pressed to see much of a difference in a blown B6/7 with all the same mods, only one is sans IM. Do you really think in head to head pulls it’d be more than half a car? It seemed the headers/exhaust manifold is where JHM was really worried with the blower.

91, you’ve got the IM right? I think you, me, and jay are the only ones with IM, blower & headers, or at least forum guys etc that I know of. (does speedtec have the IM too?)

Am I starting to sound like a B5 guy yet in the sense that more boost will just fix the problem haha.

#63

so if you’re so convinced why wouldn’t you sell it?

#64

well the tough here is how the tune is designed to limit power. cylinder pressure makes power and a better IM is going to reduce pressure losses and increase cylinder pressure for a given pressure differential/displacement/rpm/airflow system. since the IM reduces pressure losses at higher rpm when there is another artificial restriction (partially closed throttle body) that causes far more pressure loss its benefit may not be all that great since you can achieve the same cylinder pressure by opening the throttle body more.

#65

Hey Madison if you want to ditch that intake manifold…let me know. I was going to order spacers the new 034 cage and some other shit this week

beem are you saying that because the SC tune doesn’t completely open the TB, the extra flow out of the IM is not being utilized?

#66

it’s not that it doesn’t completely open…JHM just has it start to shut at around 6000 rpm to protect the motor

I have a log here somewhere…

#67

well from what I remember the throttle angle goes to like 60% (for example) open (where 100% open is the butterly parallel with the flow), it backs the throttle off. The load goal is set to something that can be reached at 60% throttle at those engine speeds so the ecu will only open the tb 60% but still meet the 100% load requested by the accelerator pedal position.

#68

with the tb partially closed you have a large amount of pressure loss across the valve, this reduces cylinder pressures (and power). So while the IM will flow better once the air is in there the large in-line restriction of the TB will negate the descrease in pressure loss in the IM.

#69

Na, like I said, I probably won’t ditch it. I like the powerdocated look a lot (so that’d be a couple hundred right there after dismantle, seals, & reassembly) along with the loss of sale price from new cost, it just doesn’t make sense. Plus, the main reason I got headers was I could stand the fact I’d done everything else and knew that the headers was the main reason everything else was being held back. Thus. . . headers went on, kinda same thing with manifold.

Good point beem.

#70

Interesting, so it would seem that the JHM manfold+ported TB combo will be good for a ton more power than they’re already being asked for.

It’s still not quite clear to me, is the stock manifold a restriction on the supercharged cars? It just seems like the charger has so much headroom that we could push the same amount of power out of a manifold made of McD straws.

#71

Well that’s kinda what Beem is saying and I stumbled around. The blower has so much head room, so the easy thing to say is just let it keep building boost and it’ll cram the air in their one way or another. My logs show it is 100% throttle angle up to 6600, and by 7000 it’s at 40% open. But at 6k, Count starts throwing some timing to help slow things down a bit. (0* from 1.5k-4k, ~1.5-2* from 4k-6k, up to 8* from 6-7k)

Power is always rising, but just slows down a bit near the top in b/c just so much air is trying to be crammed in there. The IM isn’t helping much below 5k (from my understanding) and above 4k, the blower is doing the work anyhow. That’s why the headers are so great when you’re around 3k etc, but you really feel the blower kicking in around 4-5k. Count mentioned it’s just ridiculous how much more air the blower is pushing as you reach those higher RPM’s and the rate the CMF is growing. The RS4 will be very interesting.

Obviously better efficency and lower boost for the same cfm is best, but imo, if you’re thinking about the s/c, the IM isn’t a crucial part like dp’s/headers are. I’d take that money and put it aside for the other items.

#72

yeah I think the ported intake will flow plenty past what the motor can handle with limited pressure loss

flow isnt like a set number, its an amount of flow relative to an amount of suction… so flow bench numbers dont mean an absolute limit for flow, it just means at xxx inches of water of suction such item will flow xxx cfm… if you try to flow more fluid then that number you will need to exert more suction. This translate into more pressure loss in the opposite direction (set suction with variable flow). More pressure loss, less cylinder pressure, less power.

so to add on technically anything a fluid is flowing through will cause some pressure loss, and be a restriction its just to what degree. Bends are effectively like a much longer piece of pipe when you calculate pressure drop through a flow system, same with valves etc. Look up equivalent pipe length charts…

but for example a reduction from 2" to 1" on a schd 40 pipe is like a 2.5’ foot section of pipe even though its only a few inches long… a 90* bend of radius=diameter is ~1.5’ vs a 90* bend of radius=2d (smoother bend) having a ~8" equivalent pipe length (in addition to the actual length of pipe).

the important take away from this babble is that while the normal im will have some equivalent pipe length you could never hope to calculate only meaure on a flow bench and approximate, and the ported im will have some lower number, the 40% closed TB will massively overshadow the difference in pressure loss between the ported and regular IM

the timing retard will reduce thermodynamic efficiency, not as much with flow though

#73

didnt forget about you sluts. i have everything for the build but strep throat and work have been kicking my ass. finally got to drive my car for the first time since the last video i took which was forever ago. GOD its a scary thing to drive. i have removed my rear sway bar because with it the back end gets way too light even around the slightest corner, that definitely helped and makes the car feel much more planted believe it or not. ive also taken off my 225/40/18 yokohama parada spec-2’s because they just could not handle it and replaced them with 245/40/18 Hankook Ventus Rs-3’s which so far are much much better. first time i felt what all of first was like without spinning it away lol. they are heavy though, about 26 lbs each. ouch

other than that, all is great on the car. scott has actually been driving it a lot and took it to 140 where he claims it gets there faster than your mind can comprehend. nice to hear coming from a b5 guy with twin 28’s.

hopefully now count can send me over some launch assist and we’ll be ready for big things this spring.

#74

nice choice on the RS3s… didnt realize they were making them in a 245/40 now… and carefuk with your axles lol

#75

yea i know, they were the cause of your axles giving out, thats why i went with them because i know they will grip and run nice and big unlike my other choice which we’re the Kumho Ecsta XS which run a bit small. these things bulge out past the wheel which i LOVE. plus they are super quiet and comfortable which is shocking for such an aggressive compound

#76

how many miles on them? mine used to howl badly and would pull every rock off of the road and throw them in through the windows

#77

hahaha thats awesome, i have about 75 miles on them lol but remember the weight differences of the cars. yours had to lug around 4000 lbs. mine have about 3100. id howl too if i had to support that kind of weight lol

#78

give them some miles and warmer pavement temps and see if they louden up