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Discussion Starter #1
Hi guys,

I have a Rhino 700 with cam/exhaust/MSD and I'm only showing 73 kPa of manifold pressure at WOT. Check out attached graph.

I'm wondering if this means there is power left on the table due to an intake restriction, maybe throttle body (?). Unfortunately I don't have any stock logs to compare, so I'm not sure if this is normal for the Yamaha 700 engine or if it's due to my specific mods.

Has anyone looked at their MAP pressure stock vs modified?
 

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Almost like it's hitting a rev limiter of sorts...
 

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Discussion Starter #3
Good point. I didn't plot engine speed but this is well below the 8000rpm rev limiter I have programmed in.
 

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What rpm's is this happening at? If I am reading your graph right, it doesn't state that.
 

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Discussion Starter #5
Here is MAP pressure plotted with engine RPM. The Rhino uses a CVT transmission, so the RPM jumps to peak power when 100% throttle is applied and holds there, hence the flat RPM curve in the WOT range.

The motor runs awesome with the mods I've done, just want to know if the MAP reading is in the normal range. I will probably do an intake and bored TB at some point since these motors seem to respond well to those mods. But I'm curious if low MAP may be quantitative evidence that a less restrictive intake tract would be beneficial. Ideally, adding a bored TB would show a higher MAP reading at WOT, closer to 100 kPa atmospheric. As far as I know, all NA engines should show a MAP pressure close to atmospheric at WOT. Anything less indicates there is a restriction that is creating vacuum.

I have added Stage 2 cam and exhaust, which should flow more air, but nothing crazy like Stage 3 with porting and oversized valves, etc. However, it could be that even with these mild mods, the engine isn't getting all the air it can handle.

Anyone have any info on MAP on a stock motor or built? If MAP is 90+ kPa on a stock 700 or a properly sorted built motor then I know I need a bigger TB!
 

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I may be getting older, but I refuse to grow up!
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I have bored TB's for sale if you're interested.
 

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I'm going with timing. The stock timing curve on the 700 engine is a pretty "safe" curve. RPM's fall off early so the big piston is not over worked, in turn creating less wear and tear on the engine. But if you throw a HDD timing curve on there you will see great over rev. It pulls harder and higher into the high rpm.
And yes, a bored TB will help.
If you are going for top end power that stage 3 cam would help. I had the stage 2 hot cam and enjoyed the little bottom end grunt of offered. On a bigger mechine Id go with the lower end power too.
I personally would put a 11:1 piston,bored TB and the timing curve with what you have in there now and run some 91 octane gas and be done with it. Not sure what kind of intake the rino runs but a bigger filter and tube would help. Solid build.
 

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I may be getting older, but I refuse to grow up!
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A 11:1 CP piston and +3 throttle body will add about 5-6 horsepower as well as increased bottom end, and be pump gas safe.
 

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Discussion Starter #9
Thanks guys. Do you port match the head when you bore the TB? Seems the opening on the head is the same diameter as the stock TB and rubber intake boot (between TB and head).

By the way, I put on a K&N intake and gained ~5 kPa at full throttle, so that was definitely part of the restriction.
 

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I may be getting older, but I refuse to grow up!
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In most cases the head is ported at the same time you have the head off to update compression. The TB can be added anytime. Send the rubber boot with each for porting. I have a +3 TB with a ported boot for sale if interested.
 
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