Go Back  Offshoreonly.com > Technical > General Q & A
Dyno Day!  Question for engine builders - A/F correction factor for dry dyno headers? >

Dyno Day! Question for engine builders - A/F correction factor for dry dyno headers?

Notices

Dyno Day! Question for engine builders - A/F correction factor for dry dyno headers?

Thread Tools
 
Old 05-30-2014 | 10:22 PM
  #41  
Thread Starter
Registered
 
Joined: Feb 2011
Posts: 2,640
Likes: 4
Default

My friend sometimes wishes he had picked up a Rage instead of a Heat. What were you running with the 502, mid-70's? He is getting about 63 with a 496 HO in his 28 Heat. He has talked about making some upgrades to it, but I told him to leave it alone and enjoy a turn-key boat. Seeing me walk away from him is going to make that tough on him.

The only thing I don't like about the Heat is that (at least on his boat) there is no way to close the cabin off from the cockpit and bow, so if there is a heavy rainstorm you will probably get wet in there. Also, when you get running, it acts like a wind tunnel - you better make sure all the towels, hats and can huggies are secure!
Budman II is offline  
Reply
Old 05-30-2014 | 10:57 PM
  #42  
SFOcean's Avatar
Charter Member #394
25 Year Member
Charter Member
 
Joined: Nov 2000
Posts: 534
Likes: 38
From: CA
Default

Originally Posted by Budman II
So, based on those numbers, what RPM do I shoot for when selecting a prop? 5500?
Usually about 1000 rpm over peak torque (except for light cats), so you are correct at about 5500.
SFOcean is offline  
Reply
Old 05-30-2014 | 10:58 PM
  #43  
SFOcean's Avatar
Charter Member #394
25 Year Member
Charter Member
 
Joined: Nov 2000
Posts: 534
Likes: 38
From: CA
Default

Originally Posted by MILD THUNDER
Nice run stand, I dig it! I'd probably start with the 23p mirage plus and see what you get. I'd probably shoot for 5500rpm at wot. If you rev too high, then try the 25p mirage plus. I wouldn't bother with the bravo 4 blade. Too much diameter for a deep drive setup. I'd bet ya a six pack a bravo 4 blade will kill the speed on your boat. If you want to try a 4 blade, the Revolution 4 blade works well, in applications where a mirage plus works well. The Rev is 14 5/8 diameter, but high rake and provides a lot of lift.
x2 Mild has it right.
SFOcean is offline  
Reply
Old 05-30-2014 | 11:19 PM
  #44  
Banned
 
Joined: Jun 2013
Posts: 1,014
Likes: 0
From: AZ
Default

My Rage did a best GPS speed of 78.5(had a few things done to it) with a couple bigger guys in it (myself and previous owner). I'm estimating my new engine should make around 625hp or more, so that should get me knocking on 90. The Rage is about a good 10 MPH faster than the heat. I looked at a few heats, but wanted a smaller more trailer able boat that had more speed potential with less horsepower.

Regarding the open bow, yes it can be a wind tunnel at times when left open. The rain thing doesn't apply, I live in a Phoenix and it rains here like twice a year (was about 108 here today). That being said, I have a custom support for my front cover that is usually in place and it eliminates the issue of turbulence in the mid cabin . I think Nordic hit a home run with this design. People constantly comment on the boat. And the MCOB just fits the boating lifestyle here so much more so than a closed bow. When it's Africa hot here, all a cuddy is good for is a makeshift sweat lodge to lose those last few winter lbs...

I bet you are excited to go out and surprise a few folks in yours! Things gonna rip. My cam is quite a bit larger than yours, Lift: int 654/exh645 duration 237/245 LSA 112 (dry exhaust), but I really like how you utilized the smaller oval port heads. My dart pro 1's are 275's, so not much larger than your AFR's. Oh and I'm almost at 10:1 compression. Can't wait to dyno it. Anyways enough about my project, back to your thread. Post up more pics!

Last edited by Borgie; 05-30-2014 at 11:22 PM.
Borgie is offline  
Reply
Old 05-31-2014 | 06:29 AM
  #45  
Thread Starter
Registered
 
Joined: Feb 2011
Posts: 2,640
Likes: 4
Default

Borg, you are right about the MCOB fitting the west coast boating style. My friend had a hard time finding one east of the Mississippi. I think he ended up finding his boat out in Utah. I agree about the styling of the Nordic's too - I have always liked them. Regarding the MCOB, I have always wondered why one of the boat makers hasn't made a boat with a MCOB design with a fiberglass cap to convert it back to a closed bow if needed. Add a few fill cushions in the bow and you have a forward berth = best of both worlds.

108* in May? I don't know how you stand it, although it has to be better than the sub-zero crap. I hope you guys don't run out of water out there. That drought is some serious shizit. Thanks for the good words, and good luck with your build. Looks like you have all the right parts going into it.
Budman II is offline  
Reply
Old 05-31-2014 | 11:11 AM
  #46  
Banned
 
Joined: Jun 2013
Posts: 1,014
Likes: 0
From: AZ
Default

Originally Posted by Budman II
Borg, you are right about the MCOB fitting the west coast boating style. My friend had a hard time finding one east of the Mississippi. I think he ended up finding his boat out in Utah. I agree about the styling of the Nordic's too - I have always liked them. Regarding the MCOB, I have always wondered why one of the boat makers hasn't made a boat with a MCOB design with a fiberglass cap to convert it back to a closed bow if needed. Add a few fill cushions in the bow and you have a forward berth = best of both worlds.

108* in May? I don't know how you stand it, although it has to be better than the sub-zero crap. I hope you guys don't run out of water out there. That drought is some serious shizit. Thanks for the good words, and good luck with your build. Looks like you have all the right parts going into it.
Yeah id rather have the heat any day! Cold rainy weather is depressing. The drought isn't as bad as you might think. The lakes such as Powell and the Colorado river levels are going to be something of an issue in the future if the rainfall/monsoon doesn't increase. However, all Phoenix lakes are mostly full. Why these western states haven't planned a pipeline from the pacific to purify and shuttle fresh water is beyond me. We worry about oil when the lifeblood, water is many times more crucial.

Last edited by Borgie; 05-31-2014 at 11:14 AM.
Borgie is offline  
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2026 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.