HP Pumps

[masterblaster]

can you tell from the pics with the head off how the porting looks,I have the head off now,is there any pics I can send you to tell how aggresive it is,I really dont have much experience on telling the diff? this motor looks really nice and feels tight inside.The pump really looks smooth and larger inside,very nice work,no idea how he did that.
Ive used the 13/17 concord cutt back 3 mills and repitched to a 13/15 and really wasnt impressed. I didnt notice much difference in hook up or low end over the stocker,so im gonna run this prop,your right it looks pretty much like chrome and super sharp.Im gonna put this prop and pump in my b1 and see how much diff it makes,and throw the stroker in my SJ,and see how the port feels,I hope i dont have to go messing with the port timing with machining but it sounds like a good idea if it really lacks low end.still undecided if i want to try and mess with this msd total loss or not.
Are the riva type intakes common and easy to find used? A stocker 61x wouldnt work cause they are all singles huh?It would be sweet to have the only 2 injected stroked surf boats out there not taking on water.I hear group k has a good air fuel seperator that will help with the loading up and elim the need for tank foam as well thanks for your help I enjoy the old skool stories myself

 

['Crockett]

Fuel cell foam:

Fuel/air seperation isn't really the issue with the MRD set up it's loss of prime due to fuel slosh. When the tank is full there really isn't a problem, but as the level drops the fuel starts moving around inthe tank and it only takes a small amount of air to cause the pump to run dry and lose prime.

The fuel cell foam arrests the sloshing around of the fuel in the tank. Theoretically, the fuel level just drops evenly as the fuel is burned with little or no sloshing at all. It's beneficial on carbed ski's too because the aggressive movement of the fuel in a 1/2 full tank during a race could cause a noticable change in handling. Probably not a big problem in a freestlye application though.

However, Inverted tricks could become a problem with their potential for loss of pump prime but I think the fuel cell foam along with centrifical force created by the rotation would keep fuel at the bottom of the tank for the short duration of inverted flight.


Your porting:

Looking at the ports doesn't tell you much, it really needs to mapped or at least measured from the top of the cylinder to the top of the ports so it can be compared to stock numbers.

When the piston is at TDC is the edge of the crown even with the top of the cylinder or does it actually come up above the cylinder ?


Intake manifold and related issues:

I was looking at my RIVA intake this evening, it is mounted on a motor right now and I realized that there are several clearance issue's to deal with in order to mount the 62t 50mm MRD throttle body to it. An angled reed spacer would have to be used and the adapter plate would have to be angled as well in order for the throttle cable and the metering valve portion of the throttle body to not contact the cylinder. The throttle cable would likely have to be swapped out for a Kawi version without the Yamaha cables 90 degree bend. A bracket would be fabbed so the cable would mount parralell to the cylinder and then wrap around a pulley to connect to the metering rod arm.

I am concerned after looking at it for a while that by the time you tipped everthing away from the cylinder enough to gain the clearance you needed you might end up crating a clearance issue for the FA's against the hull !

Damn, skinny assed Superjets ! . . . . .



Sorry if it sounds like I'm rambling here, I'm kinda thinking out loud as I go . . . . . in case you couldn't tell !


All these clearance issues are solvable with enough time and head scratching I'm sure. . . . . The entire throttle body could even be rotated 180 degrees so the throttle cable mounted on the bottom but a new,longer high pressure fuel line would have to be made up to reach.



Here's what's slowly creeeping into my head as I type:

Part of where the MRD system gets it's hard hit is from the short intake tract length that the "side draft" stlye mounting provides. Adding the manifold and addtional runner length might soften that hit somewhat and since the clearance issues are going to be tricky to resolve, maybe it would be better to make an effort to create an air box assembly that mounts on the throttle body to isolate it from the water in the hull and pulls it's air through a hose located high in the engine bay.

If you took a stock Yamaha FA assembly like this one and adapted it to fit the MRD throttle body you could easily fab an air intake duct or even use a flex hose to draw air from any where inside the hull.




I'll continue to look at the options for an intake manifold and or adapter plate, but I really think that a well thought out air box is going to be the practical way to go . . . . .


:biggrin:

 

[masterblaster]

That
was my thinking from the start also,I was thinking of having some sort of risor adaptor that would just raise the proks way up at a angle,but now that you mention it I think the stock SJ intake might be albe to be worked into this somehow and be even better,We find we surf riding that both styles of stocker intakes work better than anything else out there.

 

[masterblaster]

wow,just got the motor comp tested the other night,it making 212 and 215,took the head off and its got a sick looking port job with very smooth work done in transfer ports,didnt have a mic to check the distance from the top of the ports to the top of motor,the spacer plate looks to be 5 mills and the pistons come up about 2 to 3 mills higher than the top of cylinder,the head is cut back resessed but the domes have bad pit marks in them and look to have been worked over with a dremel to smooth them out,must have been from a prior motor incident,cause the pistons and sleeves look great. No matter though cause I gotta get this heads domes machined down to drop comp to 190 max.Will this effect the squish to much? will the motor still run close to as good,I just dont have the patience for going to get race gas every time I wana ride.

 

['Crockett]

Sounds like they already dropped the cylinder and recessed the head, that's a good thing for what you're doing with it !

As long as the squish clearance is o.k. then all that has to be done is recut the dome portion itself and leave the squish band alone.

I have 2 good MRD stroker head slabs on the shelf, both were for pump gas. We'd have to figure out how deep your head is recessd to know which one might work on your motor without re-machining. If you have access to a depth mic or at least a dial caliper, measure the depth from the mounting surface of the MRD head to the outer diameter of the squish band. Basically we are trying to determine the depth of the "step" before the squish band starts to taper towards the dome.

:biggrin:

 

[masterblaster]

Ah I see what you mean,I have 2 pictures I can send you that are very detailed,but right now I dont have any kind of mic.whats your email addy?also what is it that the squish does for the head again?

 

['Crockett]

The squish band concentrates the fuel/air mixture that is being compressed by the rising piston into the dome for compression prior to the plug firing and igniting the compressed mixture. So in effect, it "squishes" the fuel/air mixture from the outer perimeter into the dome area as the piston reaches TDC.

A tighter squish clearance gives you a snappier throttle response for quicker acceleration.


I'll PM you my e-mail addy . . . . .


:biggrin:

 

[masterblaster]

Ok that sounds familiar,so the tighter the squish the higher the comp then right? these domes seem to taper in right away and dont really have much of a band? So if you want to lower comp and keep the squish tight,the dome would have a pretty steep curve kinda like a bell inside then right?

Whats your feeling on these 2 factors,lowering comp from 210 to 190 for 93 oct? how much would this lower performance of a 5 to 8 mill stroker motor.like what % Im guessing its over a 5 mill stroker because of the size of the spacer plate and the additional spacing on the piston above the cylinder
secondly it has a older msd total loss,Im not sure how well it would do in salt water,so If I just run it with the msd enhancer and a light weight flywheel what % would be lost? Since you have these pump gas heads im guessing you prolly have race gas heads and prolly know the answer to these ?s better than most here.lol

sent the pics out to your email addy

 

['Crockett]

O.K . . . lot's of questions means a long response, so here we go ! . . . .


Actually, NO the squish bands main purpose is to force the fuel/air mixture into the compression chamber of the head, which is the radiused/domed shaped section of the head. This is where the actual compression of the gases primarily takes place.

It's mainly the size of this area that determines the compression.
Smaller volume = higher compression
Larger volume = lower compression

*Note:
It's a little more involved than this but I'm trying to give you a basic illustration/explanation of it.

The squish angle is roughly the same as the average angle of the piston dome at the edge of the piston. . . . . . .approx. 11 degrees on a Yamaha if I recall correctly. The width of the squish band can have an effect on engine performance also.



I have very limited experience with total loss systems, so I'm not much help there, sorry.

I have had good success with MSD Enhancers on both stroked and non-stroked Yamahas. I don't think you will even need a lightened flywheel with this Injected stroker . . . . .

Here's why:

I rebuilt a MRD injected, 5mil ADA billet stroker motor with total loss for a friends 'Blaster. I re-assembled it and test rode it and it was absolutely ridiculous ! I can't even imagine something that high strung and twitchy in a Superjet hull, I think it woud be damn near un-ridable.




From the age (vintage) of the motor combination you have it'd be my guess that it is probably a 5mil or 6mil stroker but no more. This motor with FI on it will rip on pump gas, percentages are irrelevant, this ski will be a handfull . . . . . of that you can be sure.



As measured by a compression gage I wouldn't want to see more than 175-180psi for pump gas or you risk damage from detonation. (This is another area of simplification, a compression gauge really is not the correct way to determine compression)



and one last thing . . . . .

While I appreciate the compliment, I make no claims of knowing more than anyone here or anywhere else. . . about anything.

I am not an expert, I am recreational rider and an amature engine builder who has played around with this stuff as a hobby for about the last 20 years. I have 30 years experience as a Machinist and I do virtually all my own work. I have helped several riders/friends who have raced at various levels over the years but I do not do this for a living or "for hire".

I am glad to help make suggestions and share what I have learned where and when I can . . . . . you will have to make the final decisons on what you will ultimately do with this motor.



I am trying to provide info that I think will be helpful but please remember:
When it comes to free advice . . . . . . you get what you pay for !

Seriously though, I'm trying to give you some guidance here, but you really should discuss this with a professional engine builder to verify my suggestions.


'Crockett

:biggrin:

 

[masterblaster]

hmm,well if you think this motor is gonna have that kinda hit,I might just skip the total loss and use th msd enhancer ign that already in the ski.
You seem like you know whats going on with these old school motors,thats all I meant. I have emailed tema scream to get chucks opin as well. snet you another pm about the email pics

 

[masterblaster]

I measured the recess in the head,its 2.4 mill. The spacer plate at the bottom has to be at least 3 to 4 times that thick.Ive read alot of places that a stock 62t cyclinder stroker can really only be 5 mil max. I dont get it with the recess head and the spacer plate being that thick it seems like a 7 or 8 mill or more extra stroke?