Missmatched combo performing very well?

[KnightEngines]

They both run tri-y headers...........

[peejay]

It's interesting that there isn't a torque double-bump, just a HP double-bump. The torque peaks, falls off, then starts falling off much more gradually. The RPM rise catches up to and surpasses the torque drop-off, so the horsepower peaks again.

So it isn't so much that there is a double HP peak as much as it is there is a small bump of an anomaly in the torque curve. that ends at the first HP peak.

[1mach]

by KnightEngines » Thu May 26, 2016 7:29 pm

They both run tri-y headers...........

KnightEngines , and you haven't pick this up on any other headers system just on the tri-y headers ?

by peejay » Thu May 26, 2016 6:38 pm

It's interesting that there isn't a torque double-bump, just a HP double-bump. The torque peaks, falls off, then starts falling off much more gradually. The RPM rise catches up to and surpasses the torque drop-off, so the horsepower peaks again.

So it isn't so much that there is a double HP peak as much as it is there is a small bump of an anomaly in the torque curve. that ends at the first HP peak.

peejay , Amongst my last reply i actually asked why the TQ was still dropping off? BUT then i thought i will be contradicting one of my previous statements, so i deleted the question , peejay you have a observant eye.

So here goes the question if the BHp did a double peak why didn't the TQ double peak as it is still dropping off. As all three are related to each other TQ , BHp & RPM ???

[KnightEngines]

The TQ does double peak, have a look at 5800rpm V's 5900rpm, 400rpm apart from peak Tq, same as the rpm difference from the HP peaks.
Pity we didn't pull it from a bit lower on that pull, that'd show it more clearly.

Going to have to scratch around & dig up a few tri-y & 4-1 header dyno sheets, but I can't recall ever seeing dual peaks with 4-1.

This has turned into a great discussion, learning stuff is why we're all here, from a cam mismatch that turned out better than expected to a good discussion on header design.

[1mach]

RPM-----TQ-------BHp
5800---467.5----516.3
5900---466.3----523.8
6000---467.0----533.6
6100---467.8----543.4
6200---468.1----552.5 ***** max TQ

I was trying to find the 2nd TQ peak ?

I did see that fluctuate up and down of 1ftlb of TQ bouncing around and thought maybe that's where the engine is happy at and the engine dyno run commenced as it released its 100rpm increments, engine just finding a happy medium and its starts its run.

Dint think much of it as you stated its not as clear. Pity lower RPM readings are not available from the engine dyno run.

But i would of expected the TQ to peak on the peak BHp but it doesn't so i focused more on that, the 1st and 2nd BHp peaks.

[peejay]

I see differences of 1ft-lb or so as just as likely to be measurement error/sampling margin than anything else, to be honest. Even if it was 2 ft-lb higher there instead of 1 ft-lb lower, it's still really flat there.

[cjperformance]

Hey Tony, I had a quick chat to Mike today. He would be very keen to see a back to back on the off the shelf paceys compared to the modified versions. Who knows, they may be interested in a mod if it proves very worthwhile!
On another note. Many seem bewildered at the double peaks with these engines. Assuming fairly correct pipe diameters, with 4-1's you generally never see a dual peak due to the single pri tubes only having the one 'tuned' /ideal rpm (really- gas velocity) within the engines rpm range. These tri-ys in question (unlike long tube tri ys basically 4-1's with a 4-2-1 collector) give a lower rpm tuned area for the the pri tubes v's sec tubes and collector AND a higher rpm tuned area for Sec tubes v's high gas velocity from pri tubes and collector flow restriction (aka flow velocity) so what you see on the dyno in this instance is a boosted tq area in the lower portion if the rpm range then this tames off and comes back as the secs etc come in to tune. This is what gives these tri ys such a wide tq/hp area. Yes 99% of the time 4-1's will dyno number higher at peak hp but the tri ys when working well will be very close at peak hp but tend to bring tq peak on a little earlier, so a better average will be seen. If course there are a million other factors like pipe surface area, heat/velocity retention, scavenge effect It goes on! And on! Just more to think about.

[clueless]

I do the Falcon tri ys - cut off the 2.25 collector back to 2.5 then step out to 3, they work better like that with a full system than just going straight to 3".

This is what I have found also with the VN/VK pipes. Consistently make more torque with 2.5" at the tertiary rather than 3.0". No more HP, just more torque everywhere but I have never messed with the secondary pipe size either....

CJ, how long was your 2.50" collector ? Just a choke or did it have some length ?

TK, I have seen the 2x peaks with Tri-Y pipes but have never seen a 12ft/lb jump, followed by a 9ft/lb dip like this has at 6250 !!! Weird.

[cjperformance]

Hi, just 2.5" as a choke then straight out to 3".

[clueless]

Hi, just 2.5" as a choke then straight out to 3".

Thanks, I'll try that next time !