Excellent. That should eliminate the turbo lag. You don't want to do 150mph off road any way.
Up to an est 19:1 CR (est) during break in. Not bad: the cylinders surely passed the test no question.
Getting it dialed in at race sites may be challenging; but you put it together and tuned it pretty quick though.

Looks like your research and hard work has paid off nicely.
I hope you can get a video in the future.

Thanks for your personal investment in new technology.

 

This is nothing against Scooby. I will be witholding final judgement on this unorthadox technique until we see some run time under race conditions.

However, an extra 1.4 points of compression is not going to eliminate turbo lag. It simply raises the the threshold. It will have more power before the turbo begins to produce boost and it will have even more power at every psi subsequently. The hit will probably be slightly harder when the boost starts to come on because each psi of boost with a higher starting point of compression will add more additional hp than they would at 8:1.

The cylinder has not passed the durability and reliability test yet. It has passed the short term test of running under load without failing. That is more than I expected so my hat is off to Scooby.............so far.[img]i/expressions/face-icon-small-wink.gif[/img]

I swear, I bet if I could make a pit of lava look like a refreshing pool of water, you would jump right in without even checking the temperature.[img]i/expressions/face-icon-small-wink.gif[/img]

 

DSNUT,

What are your legally credited certifications (exact name(s) please) required for you to be a home builder, and for what region(s) does this apply?


Thanks!


This should be obvious in only a matter of seconds, but if you don't have a clue:
1. wait over 4 hours and give your famous winking eye
2. change it to big grin 8.5 hours later, and then we will know you haven't been sick at home for 5 months straight.

Any editing after that is meaningless.

You should post on EXTREMEGARAGE.com forum. We never see you over there.
Many newbies with only a few posts. with new DS650's. need some information on what carbs and performance items over there. Just open a post stating the Performance Answer man is here. Bring your comrades over with you. They could probably help too!

 

[img]i/expressions/face-icon-small-smile.gif[/img]

 

Who exactly are my comrades, Phil?

PS - I am sure glad you didn't leave when asked. The entertainment value alone is priceless![img]i/expressions/face-icon-small-happy.gif[/img]

 

my turbo setup has no "lag", if you understand what that term means. any turbo has a boost rise curve which is something different than lag. lag is when you have a poor setup or too big a turbo. You open up the throttle and the motor revs way up without boost then after a slight delay the turbo spools up, that's lag.

 

Just some interesting reading.

What is turbo lag (and how do I avoid it)?
The majority of turbochargers feature a wastegate--a valve which allows some of the exhaust gas to be directed around the turbine. This allows the turbo's shaft to spin at a reduced speed, promoting increased turbo life (among other things). Think of it as a 'stand by' mode. Since the turbo isn't needed during relaxed driving anyway, this effect is harmless...

...until you suddenly want to accelerate. Let's say that you are loafing along, engine spinning 1500 rpm or so. You instantly floor the throttle. The exhaust gas flows through the turbo and cause it to spool (spin up to speed and create boost). However, at this engine speed there isn't very much exhaust gas coming out. Worse still, the turbo needs to really get spinning to create a lot of boost. (Some turbos will spin at 150,000 rpm and beyond!) So you, the driver, need to wait for engine revs to raise and create enough exhaust gas flow to spool the turbo. This wait time--the period between hitting the throttle at low engine speed and the creation of appreciable boost--is properly called boost response. Many people incorrectly call it lag, which is really something different. Lag actually refers to how long it takes to spool the turbo when you're already at a sufficient engine speed to create boost. For example, let's say your engine can make 12 psi at 4000 RPM. You're cruising along at a steady road speed, engine spinning 4000 RPM, and now you floor it. How long it takes to achieve your usual 12 psi is your turbo's lag time. Between the two, slow boost response usually causes the most complaints.

There are two aspects to consider when dealing with boost response: engine factors and driver factors. As far as engine factors go, there are many things which affect turbo lag... although most are directly related to the design of the turbo itself. Turbos can be designed to minimize lag but this usually comes at the expense of top-end flow. In other words, you can barter for instant boost response by giving up gobs of horsepower in the upper third of your RPM range. (Behold the catch-22 in designing one turbo for all uses.)

Driver factors are another matter. You basically need to understand how a turbo works and modify your driving style accordingly. To sum it up, don't get caught with your pants down! If you feel that there may soon be a sudden need for serious thrust, downshift until your engine speed is at least 3000 RPM. This way there will be noticable boost almost as soon as you hit WOT. If you are going up a hill at WOT around, say 1800 RPM and your speed is dropping, you'll need to downshift just like any other car in the same situation. Remember: turbos need exhaust gas in order to spin. Let them have some when they need it.

OMR

 

I admit, I got the term lag from traditional builders and supercharger competition.

But I did understand for a supercharger, my CR range would have been from 8 to 9.
8 being for top end; and 9 being for quicker response, but tails off on top end.

That's what I was trying to tell Scooby was 9.4:1CR was (no lag) immediate boost response, but shouldn't need 150mph top end for off- (or on-) road.

Both are superchargers anyway, except turbo's are exclusive subset with centrfugal exhaust powered blower.
Trickracing is working with root blowers which seem to have sound builders behind commercial units.

From the wrong information given, I was told that chargers were harder on engine. But starting at lower compression and scaling up and down seems to have reliability and peak perfromance potential beyond other performance enhancers: especially for touring machines. They are on 18 wheelers, etc... so they are proven economizers. My (reduced boost) maximum would be between a (9CR w/5psi) to (8CR w/7psi) @ max boost with a 12:1 CR. So starting out at 8 to 9:1 CR, there would be no low rpm knocks with pump gas. But in the end it will take experimentation to find optimal values with egt/cht meters and different road courses. Reliability will be key for me so don't get stranded on the road.

That's why I like the more primitive root charger, is it will be carbed. Dealing with carbs will be enough to work with. EFI is too bleeding edge for me, but it will be here soon for all builders to contend with in the near future. If it will work, I'll also try to incorporate dialajets for poor man's efi to help tuning sensitivity.

 

Blowers are harder on an engine than no blower at all. Where they are an advantage is your motor thinks it is bigger than it is and higher compression to.....when it actually isn't all the time. The problem with a high compression engine is, you have the additional stress all the time. A motor with a blower only has the additional stress when you are producing boost.

Yjacket, your comment about running lower boost on a supercharger with a higher starting CR is a very good point when considering the limitations of the octane you intend to run. That understanding alone will save you from a lot of the risk people take when setting up a supercharger. Another biggie will be making sure you don't get interuptions in your fuel delivery when making boost. My experience with this has been expensive and I certainly wouldn't want to see it happen to you. I wonder if there is such a thing as a fuel pressure switch that could operate an emergency wastegate. If fuel pressure drops, it triggers the wastegate to open and the manifold pressure will drop immediately protecting you from running very lean under boost. Just a thought........[img]i/expressions/face-icon-small-wink.gif[/img]

Ron

 

DSNUT,

Wastegates are for Turbo chargers exclusively, not Superchargers.

Its the only supercharger I know of being designed for DS650 engine, so I'm not going to pizz him off telling him how to do anything.
His banshee blower video sounded like a kitten at max boost (no smoke neither, just like 3.62 banshee video), so he knows what he's doing.