||02-08-2013 05:25 PM
Dynojet PC-5, with Autotune, and full exh. system Tune...
So..... It is official..... Got the notice that I will get a tax refund again this year, so I thought about starting the thread a few weeks early, as I have some questions to the lurking motor tuners here. I am ordering a set of arrow headers as soon as the refund gets here. I already have a full open pipe on it, but the stock headers are restrictive, and will be replaced. I will then hop the gs on the trailer, and take the fam to Denver,CO, and have a go at Sisneros Speed Works. The owner Eddie is a wizard in tuning big singles, and his riders have taken several titles at the PPIHC. I have known him for a while now, and he build my 55hp Susuki DRZ 470. As I arrive up there, we will first dyno the bike as a base line. I wanted to pop the stock pipe on it, and have a stock base line, but with all the crap I have on it, it would be impossible for me to start with the stock headers. So unfortunately the dyno will start with arrow headers, and open pipe. Sorry, but I dont have a shop with me, and dont want to bother Eddie with all the r&r. Then we will install the PC-5, and auto tune, and then another dyno run. Here is my concern. There have been several people doing this, but none have gotten any before and after dyno graphs.... and more importantly, not talking much about it. I also remember Joel mulling something to the fact that he had little success, or have seen none to not much gain with that setup. All that talk, is leading me to the question to you wizzards out there..... Not the ones that think they know, but the real wizzards..... Many times when you have a stock set of cams....designed for a stock restrictive exhaust system, when you open up the exhaust with out re-camming it, it will loose some torque at specially low rpm. Then it will take off at mid to higher rpm. The stock lobes are groud to satisfy the somewhat restrictive exhaust system, and now when opened, it does not work good. Thus the need for aftermarket cams. Reason I think it will work in the case of the 800, is a few indicators. First, the 800 revs very fast to start with, but is somewhat flat untill 4000 rpm, where it picks up. A race bike rips from the getgo. As my drz will leave the 8gs in the dust....until about 55 where the 8gs will pull away. The real ( to me) indicator that this should work fine, is when a fellow inmate took his 650 twin ( 798cc) and stuck the cams in there, from a 8GS..... Although it ran, you could hear the now more aggressive lobes made that thing run hard at idle, and at pick up. Sort of like a race engine. Very rough idle. When I saw that video, I had a feeling that the lobe grind of the stock 8GS came are good enough to open up the exhaust. We shall see, but whatdayathink.....
(ps) Thanks to DWS underneath, for pointing this out. I forgot to mention that we will also focus on the intake side, as I clearly thinks that the 8gs is restricted with those long funky snorkels. So one dyno run in the end with the airbox cover off, should decide that.