"The Mongoose" - 1 3/4" Headers To 1 7/8" Headers (447 rwhp and 431 rwtq)
04-28-2016, 11:12 AM
#63
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I understand what ddnspider is saying, with the valve timing, but I don't know if I would blame that. Although it is all about combination & it may be. Just my thoughts. So when overlap is happening the piston is around TDC. If the exhaust velocity is there it should help expel more exhaust & bring in the intake charge before the stroke. Then exhaust valve closes & intake stroke begins. In my mind I see those 1 3/4 headers giving a more broad tq curve at higher rpm. Better efficiency/ability at that engine speed. The 1 7/8 header gained great low/midrange tq. Maybe something with the design for this combo. It seems the efficiency is not there up top. Maybe at that certain rpm, 5800 or so, the headers make some sort of turbulence that brings the velocity down & then the overlap is actually hurting power.
Last edited by SoFla01SSLookinstok; 04-28-2016 at 11:51 AM.
04-28-2016, 01:50 PM
#66
Brian Tooley got back with me, and here is what he said:
Looks like classic over scavenging. The Dart heads tend to have a LOT of exhaust flow, which is the root of the issue.
We back to back tested 1 3/4" and 1 7/8" headers at TFS. On heads with stock 1.55" exhaust valves the 1 7/8" were better everywhere, the TFS heads with their 1.57" exhaust valves made about the same power with both headers and the AFR 205 heads with 1.60" exhaust valves made less power with the 1 7/8" headers.
Installing a better breathing intake like a Fast 102 would benefit.
Brian
When you look at the flow numbers for these AI Dart/RHS heads, they do have extremely good flowing exhaust numbers compared to most other aftermarket CNC'd heads. Exhaust valve size on my heads is 1.575". Honestly, they very closely resemble how the AFR heads flow, so what he says makes sense.
Looks like classic over scavenging. The Dart heads tend to have a LOT of exhaust flow, which is the root of the issue.
We back to back tested 1 3/4" and 1 7/8" headers at TFS. On heads with stock 1.55" exhaust valves the 1 7/8" were better everywhere, the TFS heads with their 1.57" exhaust valves made about the same power with both headers and the AFR 205 heads with 1.60" exhaust valves made less power with the 1 7/8" headers.
Installing a better breathing intake like a Fast 102 would benefit.
Brian
When you look at the flow numbers for these AI Dart/RHS heads, they do have extremely good flowing exhaust numbers compared to most other aftermarket CNC'd heads. Exhaust valve size on my heads is 1.575". Honestly, they very closely resemble how the AFR heads flow, so what he says makes sense.
04-28-2016, 02:08 PM
#67
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And that's why brian makes good money at this! Maybe a decent follow up question. If the exhaust is over scavenging, would that cause the intake to be at a lower pressure, but then putting a better intake on allows it to reach higher pressure at WOT?
04-28-2016, 02:16 PM
#68
A) Get a new cam that he specs out for me
B) Get a FAST 92/92 setup.
He wrote back and said to leave the cam and get a FAST setup.
By the way, that's why I really like Brian Tooley. He always takes the time to answer my questions and wants to assist you with what's in "your" best interest, even when it means not making a sale. That means a lot to me.
04-28-2016, 03:24 PM
#70
I asked Brian which would be more beneficial to me:
A) Get a new cam that he specs out for me
B) Get a FAST 92/92 setup.
He wrote back and said to leave the cam and get a FAST setup.
By the way, that's why I really like Brian Tooley. He always takes the time to answer my questions and wants to assist you with what's in "your" best interest, even when it means not making a sale. That means a lot to me.
A) Get a new cam that he specs out for me
B) Get a FAST 92/92 setup.
He wrote back and said to leave the cam and get a FAST setup.
By the way, that's why I really like Brian Tooley. He always takes the time to answer my questions and wants to assist you with what's in "your" best interest, even when it means not making a sale. That means a lot to me.
04-28-2016, 03:30 PM
#71
Brian Tooley got back with me, and here is what he said:
Looks like classic over scavenging. The Dart heads tend to have a LOT of exhaust flow, which is the root of the issue.
We back to back tested 1 3/4" and 1 7/8" headers at TFS. On heads with stock 1.55" exhaust valves the 1 7/8" were better everywhere, the TFS heads with their 1.57" exhaust valves made about the same power with both headers and the AFR 205 heads with 1.60" exhaust valves made less power with the 1 7/8" headers.
Installing a better breathing intake like a Fast 102 would benefit.
Brian
When you look at the flow numbers for these AI Dart/RHS heads, they do have extremely good flowing exhaust numbers compared to most other aftermarket CNC'd heads. Exhaust valve size on my heads is 1.575". Honestly, they very closely resemble how the AFR heads flow, so what he says makes sense.
Looks like classic over scavenging. The Dart heads tend to have a LOT of exhaust flow, which is the root of the issue.
We back to back tested 1 3/4" and 1 7/8" headers at TFS. On heads with stock 1.55" exhaust valves the 1 7/8" were better everywhere, the TFS heads with their 1.57" exhaust valves made about the same power with both headers and the AFR 205 heads with 1.60" exhaust valves made less power with the 1 7/8" headers.
Installing a better breathing intake like a Fast 102 would benefit.
Brian
When you look at the flow numbers for these AI Dart/RHS heads, they do have extremely good flowing exhaust numbers compared to most other aftermarket CNC'd heads. Exhaust valve size on my heads is 1.575". Honestly, they very closely resemble how the AFR heads flow, so what he says makes sense.
04-28-2016, 03:36 PM
#72
Nice to hear from someone who does it for a living that I was on the right track....the funny thing is I put all your cam/head flow data into 1 of the virtual engine dynos and your HP curve looked just like your posted dyno graph and you peaked at ~420hp. I started messing with the "exhaust setup" and changed it from shorty headers to long tubes and the dyno graph looked the same, just changed the peak....like your 1.75 to 1.875 header swap did...I take those engine simulators with a grain of salt, but it was pretty funny to me how close it was.
Well, I did learn something throughout this process. The better the exhaust flow of the heads, the less need of bigger primary headers, i.e. AI Dart/RHS heads, AFR heads, etc. Heads with stock size exhaust valves, or exhaust valves not exceeding 1.57", either saw improvement or no difference at all going from 1 3/4" headers to 1 7/8" headers. Anything over 1.57" sized exhaust valves made less power with 1 7/8" headers.
Last edited by Rise of the Phoenix; 04-28-2016 at 03:41 PM.
04-28-2016, 03:49 PM
#73
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It makes a lot of sense. With your TQ numbers where they are, when you get s proper 6300 rpm peak, your HP will look more in line with where it should
04-28-2016, 04:08 PM
#75
The interesting thing is, assuming you could do your own engine work, you'll have at least $800 into a FAST setup, and a new cam is what $350? It's be interesting to see if a different cam would make more or less power than the existing cam with a FAST. I would assume the FAST, but it is curious just thinking out loud
04-28-2016, 04:13 PM
#76
The interesting thing is, assuming you could do your own engine work, you'll have at least $800 into a FAST setup, and a new cam is what $350? It's be interesting to see if a different cam would make more or less power than the existing cam with a FAST. I would assume the FAST, but it is curious just thinking out loud
04-28-2016, 05:20 PM
#78
This is a very interesting read, thanks for sharing!
When I added a ported FAST92/92 I only picked up 10rwhp. This was after a complete retune of course.
I did have AI 226 heads with the TSP Torquer 2 cam and 1 3/4 headers... Will be interesting to see what you pickup... $1200 for 10whp was pretty upsetting LOL but when its about all out performance every little bit counts as we all know...
When I added a ported FAST92/92 I only picked up 10rwhp. This was after a complete retune of course.
I did have AI 226 heads with the TSP Torquer 2 cam and 1 3/4 headers... Will be interesting to see what you pickup... $1200 for 10whp was pretty upsetting LOL but when its about all out performance every little bit counts as we all know...
04-28-2016, 07:05 PM
#79
"The Mongoose" - 1 3/4" Headers To 1 7/8" Headers This is a very interesting read, thanks for sharing!
When I added a ported FAST92/92 I only picked up 10rwhp. This was after a complete retune of course.
I did have AI 226 heads with the TSP Torquer 2 cam and 1 3/4 headers... Will be interesting to see what you pickup... $1200 for 10whp was pretty upsetting LOL but when its about all out performance every little bit counts as we all know...
When I added a ported FAST92/92 I only picked up 10rwhp. This was after a complete retune of course.
I did have AI 226 heads with the TSP Torquer 2 cam and 1 3/4 headers... Will be interesting to see what you pickup... $1200 for 10whp was pretty upsetting LOL but when its about all out performance every little bit counts as we all know...
04-28-2016, 08:58 PM
#80
Just a little food for thought: If you haven't heard of the Engine Masters Challenge, these guys are building engines and competing for best horsepower and torque per cubic inch in an RPM range of what a typical street engine would see (6-7k RPM). SAM built a 436ci LSX that made 727hp at the flywheel using a 240/252 cam with a 100 LSA.