Seca Turbo System Thought

This is just a thought I had floating around in my head today and would like some input from the Seca Turbo Gurus.

My understanding of the reed valves and BOV system on the Seca:

Reed valves - open in conditions of no to low boost pressure and allow the engine to draw air directly from the air box via the small connector tube, essentially bypassing the turbo. When boost pressure reaches a certain level in the surge tank, the reed valves are forced closed allowing the turbo to feed the air to the engine.

BOV - Opens at preset level, resulting in the reed valves opening, and air being drawn in from the air box via the small connector tube. This in combination controls the turbo boost pressures.

Is the above correct, or close enough?

Now, my thought.

1 - Remove reed block and BOV from surge tank.
2 - Fabricate block off plate, with mount for an adjustable BOV (car type)
3 - Ditch air box, attach air filter directly to turbo. Or, fab piping to mount filter in vacant space where air box used to reside.
4 - Pipe for intercooler and add intercooler to system.

What would the results be? Seems to me, that the factory system could be modified some to possibly gain a few more hp. I'm not looking for Turbo Busa performance or anything crazy. If that's what I wanted, I'd build one.

If this is won't work for whatever reason, please let me know and discuss options.

Thanks,

Randy

 

I have found some good info on http://turbomotorcycles.org/

I did find a few things outside of that site though.

Remove the restrictive air box that supplies air to the turbo and the airbox. Add a filter directly to the turbo.

The air intake on the surge box should remain there. Add a filter directly to the opening. I did this on my bike. Low end torque and boost was considerably better.

The reed valves and BOV look like they could be modded to accept a full rack of reed valves vice the three little ones in there. This will do away with the internal BOV. I looked at some reed valve setups on ebay and the reed valves from a snowmobile look like a good fit.

I found that an intercooler from a Capri XR2, Probe GT or 626 GT is about perfect in size and has the correct angles on it to run your intercooler piping. You can find or make flanges to accept the inline BOV. There still some yards around that will have these cars around. The stock bypass/BOVs are good for about 15-18psi anyway, but not adjustable.

 

wish i could help,but this stuff goes way over my head.its an interesting idea tho.when u say it may give higher bhp,is that a higher top figure? or higher lower down the revs?
im only guessing here,but is the idea with your modifications to get the turbo to cut in sooner?

 

The intercooler will probably increase spool time as the turbo isn't sized for a long distance of pipe coming from the intake. Top end power should increase but that will depend on fueling and peak boost pressure. you might have a hard time finding a automotive BOV that will open at the low psi that you will need to have to run. Also Idle issues may pop up from that bypass removal.

 

What would work better than an intercooler and be easier to fab is a water/meth injection system. It would be a bit of a pain to find a location for a tank but it would save space and alow for much more boost assuming the stock turbo has more boost to give.

Disclaimer: I have no idea on the size of the turbo on these bikes or boost psi that they run judging by the size I see in pics and the motor size of the bike I'd imagine that around 5-7psi is being run and the turbo has room for probably 10.

 

The reed valves permit the idle and off boost running. The internal BOV only vents excess pressure at 15psi. Doesn't affect idle. The cone filter added to the surge box helps low end response and boost transition. The turbo runs out of efficiency after 15psi but have ran mine up to 18psi with the intercooler. the water/meth injection would be sweet. The only drawback is the size of the water/meth container and having to refill it or remember to refill it. The I/c is there all the time. The setup can be had for cheap at most yards. Ebay has 1.75 intercooler piping kits and flanges are also available for the BOV. I installed the BOV just before the intercooler and then switched it to after intercooler. The after intercooler feels more responsive by seat of the pants dyno. The turbo is a Mitsubishi TC03, but a TD04 hybrid (TC03 hot/TD04 cold) would be more efficient setup. Even the VJ11 from the Capri/323gt would be a nice upgrade with an aftermarket header and flange. I highly suggest hogging out the exhaust ports for better flow. The valves from a N/A 750 or 900 in the turbo head would be a good idea also as they are bigger than the 650 turbo valves. I have been toying with the idea of using a MAxim X motor with the 5 valve head and utilize two bas and head gaskets. The carbs woud need a spacer/adapter for them to mate up, but would be a real screamer under boost. I found this info on turbomotorcycles.org :

The Maxim X motor shares a ton of bottom end parts with the XJ motor. So 900 crank rods and pistons in a Maxim X block topped off with the Maxim x head would be a real Busa killer or at least give it a run for its money.

 

That would be a wild set-up, but the shaft drive XJ's are limited to 140 MPH due to overall gearing -

And the Turbo 'Busa does wheelies at 190 - - in the RAIN !!

http://www.youtube.com/watch?v=ud_gXPCMUDw

(don't nobody ride like this)

 

I have had my XJ750XN on speedo at 145 with maybe a little more left,but no cahoona's left. Don't know how close the speedo is at that speed. Still nowhere close to 190,no thanks on that one. It would be fun to turbo a XJ750. Gives me some thing to think about,it would be a one of a kind!

 

I should have been more specific about the Busa comment. I should have said a run for the money in the 1/8 or 1/4 mile. A N/A Busa not a turbo Busa. Yeah the top speed is limited for us on these bikes to about 140-145? With the 900 bottom end, Maxim X head and turbo it will get there real quick!

 

Oh yeah the last thing is, the Yamaha carbs are not as big of a need than initially suspected. Check this website out about boosting CV carbs on an R1

http://www.turbo-bike.net/

 

Pretty much looking for more low end.

I'm trying to avoid opening up the motor if possible. This bike is a low mileage survivor. Water/meth wouldn't be too hard, you could repurpose one of the storage pockets on the fairing and mount a tank in there. It would be small though. I have thought about an intercooler, but with the added piping it would probably increase lag.

As far as deleting the reed valves, the engine should still have plenty of air at low boost and idle breathing directly through the turbo. They just seem like very small air openings.

Everything I want to do must be easy to reverse and put the bike back to stock. I'm also working on fitting a 96 GSXR 750 front end on it. I've got a spare set of forks and trees, and can build spacers and bushings to keep the stock front wheel. I may look into a turbo swap also. I've already started collecting parts to rebuild the collector and I've got a Dan Moto GP pipe that I was going to use on my GS750, but used a Vance and Hines setup instead.

 

come to think of it, I have a stock turbo from a 90's Supra twin turbo laying around. I'll have to look it up and see what the specs are. The only other turbos I've got are HX35's and a couple of HT3Bs. There is no way you could ever spool them on a bike.

 

come to think of it, I have a stock turbo from a 90's Supra twin turbo laying around. I'll have to look it up and see what the specs are. The only other turbos I've got are HX35's and a couple of HT3Bs. There is no way you could ever spool them on a bike.

 

You will sacrifice low end power blocking off the reed valves and just trying to rely on the turbo to make the power. I tried that already on these bikes. The low end SUCKS with the reed valves blocked off. It takes forever for the turbo to spool. You need the filter on the surge box. The reed valve swap is very tempting for the idle/off-boost transition.

As far as the opening the motor, I hear you on that one. If you can get a donor Maxim or 900 you can use that motor for the build and save your low mileage motor for an easy swap back to stock. The alky injection is doable. Plenty of room in the big turbo fairings. I like the intercooler setup, but the I/C and alky injection together that would be awesome!

I don't know if you found this already or not, but go to www.ohiocaferacers.com and click on "TECH" it gives a great list of front ends and stem sizes for swaps, then go to www.goallballs.com for the stem bearings. The Gisxer set up is spot on. Try to find a Vision 18" front wheel or get the Seca 900 rear (2.75" wide) and a 16" or 17" FJ1100/1200 front (2.75-3.00) This will give you a better tire selection.

 

If you haven't looked at this site already, you really need to. It is an excellent source for turbo ideas and setting one up. The big R1 with the big turbo even has a breather valve on its surge box to assist in idle/off boost transistion. The valve install yielded a much better boost response at a MUCH lower RPM. 3000 vice 4500. If you could find a way to make and install a valve like the R! valve, I bet the reed valve removal would be a great idea at that point. I was looking at the reed valve upgrade for the same reason you are, the reed valves in our bikes are very small, but if not there or something that acts similarly, you will be killing your low end response.

Check it out

www.turbo-bike.net/

The tiny turbo carbs on our bikes could be replaced with some bigger CV carbs from a late 70's Honda CB750. The carb spacing is about the same as our bikes. Use the inputs about boosting the CV carbs on the R1 site.

 

just because a bov will hold 15-18 psi does not mean it will not operatie below those pressures. usually a bov is controlled by a vaccum source. when the turbo produces positive pressure it holds the diaphram or piston within the bov closed via a vaccum line. when the throttle plate closes and the engine is in vaccum, the diaphram or piston is drawn open again.

 

Yes that is true on most of the BOVs I have used (auto type- Greddy Tial, Apexi all work that way) The BOV in our bikes do not. They are either venting pressure or they are closed. They don't bypass air under vacuum. That is why the reed valves are there. There is no vacuum source to the internal BOV. It is set to blow at 15-18 psi in the surge box without the need for a vacuum soruce. It's more like a wastegate than a BOV. I got mine to hold to 18 psi by crushing it a bit in a vice, like the DSM guys do on stock BOVs.

 

somebody had mentioned the use of an intercooler/bov from a car, hence why i posted.

 

If he were to run an auto type BOV he could have it blow at any psi he wanted under vacuum as long as it was adjustable. The more I look into this, I am feel the snowmobile reed valve upgrade or the R1 valve would be very beneficial. I have a turbo Ford 300/4.9 straight six project I must finish first. I really feel there is some more power down low in these motors without digging into them.

 

Strat,

I had to re-read your post. If he were to run a "BYPASS" valve it "MAY" circumvent the need for the reed valve set-up in the surge box.

The Gillis Valve used on the Mustang SVO/Merkur XR4Ti or maybe a stock Saab/Volvo bypass is best suited for this I think. I draws air under vacuum and closes under boost and re-opens when engine goes back to vacuum. It is all plumbed into the air filter plenum just before the turbo.

So yes, in theory, the reed valve delete would work, I don't know why I didn't think of that before. I guess I needed a nudge to think more about it.

Nice input, just took me a minute to get my mental ROLODEX in order.
Sorry if I came across the wrong way, I was thinking in the box, not out of it.