M`cycle Turbo primary pipe length?

[stay`tee]

in the old days the american turbo pac kits had an exhaust log similar to what ack attack now runs, then thay went to a collector set up ( primary pipes at a certin length into a collector just before the turbo),, these days on the modern sports bikes we see primaries as short as thay can be  made to get the turbo as close as possible to the head...
i have always set my turbos up based on the primary/collector system, reason being that i think that it can deliver better  flow along with pulse to the turbo,,, what say ye gentleman???

[Stainless1]

The short primary tubes are used to keep the turbo above the oil level of the pan to eliminate the need for a scavenge pump.  I read an article in the 70s Renault did a tuned turbo exhaust for racing, HP was improved considerably.  Of course, the Busa motor is up to 600 to 700 HP on the dyno these days with the short primary tubes, how much more HP would you like... 

[ddahlgren]

Stainless you know the answer I want all of it LOL.. In all honesty the turbo Nissan, Lancia/Ferrari etc.. GTP cars I work on have a very complete header system along with very NA looking tuned intakes and make gobs of power .. less per cc than a hayabusa per cc but with less boost and can do it until you are tired of pouring fuel in the tank along with a torque band that looks like an electric motor. A 24 hour race is just another race for them. 5 seconds on the dyno is nothing. I am willing to bet most of the 650+ hp bikes are dyno queens to be honest. I have dynoed my share of them and never found that power with anything that would live for 5 miles.. Saying that it does remind me of the 80's F1 shootout where 1500 hp from 1500 cc's was possible but the boost levels wild and crazy and still not a 5 mile pull a squirt on a straight and then a rest in a turn..
Dave

[Hans Blom]

I'm a big believer in 'real' primary pipes for turbo exhaust. It's not like you would consider having a less than optimal pipe design anywhere else in the system, be it a turbo or NA motor. Flow is Flow. Dave your comment on 5 seconds of dyno time made me smile. This should be it's own post question...but what do some of you guys do in the dyno room??? Our dyno guys in Houston where climbing up the walls when we were dynoing our E motor for the GMR 23 T(little yellow one, Contrivance Engineering, #920) If you can immagine the blistfull noise of a 260ci sbc(na) screaming at almost 9000 rpm making 2.2hp per cube....for one minute...Our thought was if we are going to break it, do it in Houston, not at Bonneville...that motor gave the first red hat.

[ack]

in the old days the american turbo pac kits had an exhaust log similar to what ack attack now runs, then thay went to a collector set up ( primary pipes at a certin length into a collector just before the turbo),, these days on the modern sports bikes we see primaries as short as thay can be  made to get the turbo as close as possible to the head...
i have always set my turbos up based on the primary/collector system, reason being that i think that it can deliver better  flow along with pulse to the turbo,,, what say ye gentleman???

Sometimes expediency trumps proper design.  Especially if you have power to spare and your goal is to GIT-R-DONE . 

[Hans Blom]

ack is correct, time and space are a bitch...but I think we all will revel the day we have too much power! Some day......

[hawkwind]

Ronnie,  ACK hit the nail on the head ,for me the hardest part of a build and the most time is consumed working out the spatial relationship of all the parts ,in the end everything is a compramise (at least for uneducated engineering bums like me ) .of all the things the big dog LSR bikes lack , HP is not one of them ,traction is ,solution in my case ,place maximum effort in aerodynamics ,build a less stressed more reliable WOT engine .
anyway hows your new lsr bike comming along ?
gary

[stay`tee]

hay ack, i wasn`t having a shot at you about the primary pipe, was only thinking of it as an example to what i was trying to say (convay), sorry , i can now see how it could be taken the other way...

[stay`tee]

gary, regards your question,, at present i am busy with dragracing here in the north,and work on my ls project as time permits,, i was having issues fitting the turbo using calculated primary length, hence this thread, to try and gague if the present trend of putting the turbo up close to the head held any added advantage,, yes everything is a compromise, but dont ever be afraid to ask
btw, have come up with a way to mount the turbo with primary`s

[ddahlgren]

A couple of things to keep in mind.. The correct primary length changes with altitude same goes for the intake system as air density is a determining factor there. So do not use some of the tradtional calcs that assume an air density they will be wrong with a turbo engine.

Dyno time, figure out at the target speed how long you will be in high gear and don't bother doing a stress test much more than 50 to 75% of that. In the lower gears you are loading the engine down and even in high gear there will be some slip even if only occasional. A dyno is a zero slip device like pushing down a concrete wall. On a superflow dyno 100 rpm per second is plenty slow enough over the rpm range of interest. I have been asked in the past to tune bikes on a chassis dyno with a 2 second pull.. blip and over what was that? LOL When changing the preload of the bike or tire pressure becomes a tuning tool I surrender..

Some thoughts at least open for debate but the way I do it if any are interested..

[4sfed]

Dave your comment on 5 seconds of dyno time made me smile. This should be it's own post question...but what do some of you guys do in the dyno room??? Our dyno guys in Houston where climbing up the walls when we were dynoing our E motor for the GMR 23 T(little yellow one, Contrivance Engineering, #920) If you can imagine the blistfull noise of a 260ci sbc(na) screaming at almost 9000 rpm making 2.2hp per cube....for one minute...Our thought was if we are going to break it, do it in Houston, not at Bonneville...that motor gave the first red hat.

Sounds like the dyno operator I had to train.  I like to make the final run at peak hp and watch the torque meter.  It should climb a couple lb-ft as the oil gets warmer.  Any drop could indicate borderline detonation, etc.  I explained my plan to the dyno operator and told him I wanted to load the engine and hold it at peak hp for one minute, unless the torque started to drop.   It took three tries.  On the first run, someone in the shop, loading parts in his truck, slammed the tailgate . . . the noise was interpreted as impending failure and the engine shut down.  On the second try, the office door was slammed shut because the owner was trying to make a phone call . . . another loud noise!  Finally on the third try, I put my hand on the guy's shoulder and told him I'd remove it at the end of one minute.  The poor guy had beads of sweat on his forehead! 

[Harold Bettes]

Howdy All,

The dyno stories of all types are dear to my heart. A good tester-operator has to be skeptical and tough at the same time if good data is the goal.

I have written a book on Dyno Testing and Tuning with co-author Bill Hancock. It is available from any number of sources including the publisher www.cartechbooks.com. This is the first time all this kind of information has been between two covers. The book covers test procedures and various corrections and other details that are targeted for gearheads. The book is written in a generic fashion so that it can apply to all types of test equipment (dynos), both chassis and engine types.  This is not intended to be a crass commercial, but wanted to call your attention(s) to its availability. You can go to Barnes and Noble and see if they have any on the shelf. IF they do, you can sit down and read/scan through it and decide if it is of interest to you.

The comments about 100 rpm/sec are spot on. Takes some stones to get used to laying the throttle down and letting her eat for a while, but that is the way to get some really good data. A great time to smack a steel plate with a hammer if anybody has a sense of humor, but it gets pretty dicey doing that!

Now I am writing another one about airflow through engines and flow benches, too. Should be out toward the end of the year (I hope).

Regards to All,
HB2

[Dynoroom]

Sounds like some fun reading around the campfire at the bend in the road this summer.......

[ack]

hay ack, i wasn`t having a shot at you about the primary pipe, was only thinking of it as an example to what i was trying to say (convay), sorry , i can now see how it could be taken the other way...

No offence taken.

I was just trying to point out if I was trying to get the most horsepower possible I would build the best normally aspirated motor I could and then put the turbo on it and start experimenting with header pipe lengths going into the turbo leaving the intake track alone.  The Hayabusa does a pretty fair job of making normally aspirated power stock.  With a few modifications to the stock engine JE Pistons, Carrillo rods, and APE valve springs, Motec ECM and larger hold down studs the motors with the proper turbo set up will make 500+ HP each and be fairly reliable.  We have only put down about 450-500 HP to the ground so building a motor for maximum performance would have been an overkill.

You coming to any of the US events this year?

[panic]

This is a fatal character flaw in most good designers: the compulsion to do everything to the limit of known science.
The problem is that (as a famous maxim from the Romanoff days) "perfect is the enemy of good enough".