Back from the Dyno (Need Advice)

[sheerider11]

I have another set of cylinders sitting around, I might have those ported and move on.

 

 

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Woah wait. Double check your domes.

Make sure they are what they need to be.

May possibly be over ported. But before you deem the cylinders junk, double check the parts

[Bennett131]

Your engine setup isn't working.

60hp out of a 4mil with 50/50 fuel is terrible. It also peaking before 8500 isn't a good sign when you have shearers.

What is your clutch setup?

That same guy argued with me about T5 pipes for a long ass time on fb. Not suprising.

[Bansheeandy]

Check your squish Are you running Kevins cranks ?

[Surfrjag]

Why didnt you ask wicked to look into your issue while it was there?

[danny]

We talked about what could be off, he seemed to believe it was the port job. Either way, I'll take it out next weekend see if I notice anything else. Just wanted to give everyone a quick update.

 

 

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[guns4children]

You could also say you're going to let me give your gf a nude back rub.

[guns4children]

I need you there to whisper to me in French.

[trickedcarbine]

^ that's sexy.

[danny]

Thanks everyone, talked to Kevin, he's sending me a new set of domes. I'll keep you updated.

 

 

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[blowit]

While the head is off, I would take the opportunity to take a few pics with the pistons down AND use a digital caliper to determine the height of all the ports.  With that information, I might be able to point you in the right direction.  I am not convinced domes are going to get you the missing 15hp, but you might have a combination of factors....mainly the ports don't match the pipes.  That is what is looks like to me so far. 

 

Also, make damn sure when your pistons are at BDC, the piston timing edge is flush with the bottom of the ports.  It's important. 

 

Also, once you have all this figured out and get your jetting right, you may want to start pushing on the timing.  Many people get stuck using canned values you find on the Inet.  Every engine is a little different and we have some wanting about +10*.  If the engine responds favorably and the plug is looking good, keep pushing it. 

 

Brandon

Mull Engineering

[J-Madd]

While the head is off, I would take the opportunity to take a few pics with the pistons down AND use a digital caliper to determine the height of all the ports. With that information, I might be able to point you in the right direction. I am not convinced domes are going to get you the missing 15hp, but you might have a combination of factors....mainly the ports don't match the pipes. That is what is looks like to me so far.

 

Also, make damn sure when your pistons are at BDC, the piston timing edge is flush with the bottom of the ports. It's important.

 

Also, once you have all this figured out and get your jetting right, you may want to start pushing on the timing. Many people get stuck using canned values you find on the Inet. Every engine is a little different and we have some wanting about +10*. If the engine responds favorably and the plug is looking good, keep pushing it.

 

Brandon

Mull Engineering

What is the significance of the piston edge being flush with the bottom of the ports at BDC? I have seen motors where that is not the case. One of them may have had issues, I don't recall.

[blowit]

On a 4mil stock cylinder, the piston will travel 2mm further down thus the need to lower the ports as well.  Not doing this can result in an eddy current setting up at the bottom of the port causing turbulence.  In general, it helps the port flow. 

 

I mention this because of the disappointing dyno numbers.  There might be something lacking in the porting. 

[J-Madd]

On a 4mil stock cylinder, the piston will travel 2mm further down thus the need to lower the ports as well. Not doing this can result in an eddy current setting up at the bottom of the port causing turbulence. In general, it helps the port flow.

 

I mention this because of the disappointing dyno numbers. There might be something lacking in the porting.

Hmmmm. I may have to revisit some things on one of mine that I think may have this issue.

 

I was told it didn't matter. ..and I guess I just believed that and went on.

[J-Madd]

Brandon,

 

Do you have a link to some calipers that fit in the cylinder or do you just cut a set down?

 

I need to double check some things in another motor. I usually just use a degree wheel, but this motor is apart.

 

 

Edit: I think I found some on Amazon that are only about 60 mm wide so nevermind.

[blowit]

I am sure there are plenty of engines making power without that port adjustment and I don't mean to start any hot debate about it because there are lots of factors that go into ports.  Factors just as turbulence in the port tube, velocity, pressure delta, etc.  All things which I have learned that porters don't care about learning.  Just move material around until it goes faster. 

 

No doubt even at the engineering level with OEMs, they have played around with countless theories of design. 

 

Lowering the transfer port makes the window bigger.  This will reduce flow velocity on top of the piston.  General physics principal indicates as we decrease velocity, pressure will increase so we will have a more dense charge. 

 

As well, depending on the actual velocity of the port flow, there will be a wedge shaped eddy of turbulent charge at the edge of the piston that likely does not get fully charged up with fuel.  There are 4 transfer ports!  That is a lot of volume. 

 

If there is one thing to learn with subsonic airflow, it is to keep all edges smooth, rounded, and no abrupt obstructions or cavities.  When I see people knife edge the intake bridge, I realize someone did not do enough reading before grabbing a porting tool....