G/GC record Unblown Gas Coupe "G" 2018 191.8 mph

[Stan Back]

Thanx, Rex, for the above rundown. 

Stan

[jacksoni]

Scott- The base engine is based on- think- a ZR800 Arctic cat sled engine. Bore and stroke are 81x76 for just under 400cc/. The pipes were built per my engine guys specs ( more power would be available if were a drag sled both in tune and pipe design but he felt would not live 5 miles) with the idea that I needed a broader power curve, since as Rex points out, and I looked, there is no such thing as a really close ratio (that you can pick) that is affordable,  multispeed transmission. He kept saying I needed a 6 or 7 speed, and I kept saying there is no such animal. Ok I found some sequential thing that might have been close but was nearly $20K. Not happening. I do have a G Force 5 speed that has nearly unlimited ratios available and have them, especially the 4-5 shift, very close. Power range is close to 1000 rpm and that is about the drop in that last gear. Press together 5 cyl 30+" long crank........

Anyway, if I knew how to tune it and stopped messing with the tune I'd be better off. Last year my data logger worked on one run. Then there was the odd driver screw up forgetting to turn it on. etc

So am freshening the engine and we spent lot of time in wind tunnel last week with two cars. The Nissan lost the race......   If we were only racing dynos and wind tunnels and computers be much better off. 

[Stan Back]

Here are two thoughts, both of which take almost no money . . .
(Take them for what they're worth from a exStreet Roadster guy.)

1.  As your engine is, I guess, more or less, separate engines, tune a couple of cylinders for higher rev outputs and maybe they'd carry the lesser ones along. (Wow, is that crazy, or what?)

2.  Tune 'em all for higher end increased output with a closer range gears in a 4-speed and push the car to the one.  (This would not be an option for El Mirage.)

[Hot Rod Lincoln]

Scott- The base engine is based on- think- a ZR800 Arctic cat sled engine. Bore and stroke are 81x76 for just under 400cc/. The pipes were built per my engine guys specs ( more power would be available if were a drag sled both in tune and pipe design but he felt would not live 5 miles) with the idea that I needed a broader power curve, since as Rex points out, and I looked, there is no such thing as a really close ratio (that you can pick) that is affordable,  multispeed transmission. He kept saying I needed a 6 or 7 speed, and I kept saying there is no such animal. Ok I found some sequential thing that might have been close but was nearly $20K. Not happening. I do have a G Force 5 speed that has nearly unlimited ratios available and have them, especially the 4-5 shift, very close. Power range is close to 1000 rpm and that is about the drop in that last gear. Press together 5 cyl 30+" long crank........

Anyway, if I knew how to tune it and stopped messing with the tune I'd be better off. Last year my data logger worked on one run. Then there was the odd driver screw up forgetting to turn it on. etc

So am freshening the engine and we spent lot of time in wind tunnel last week with two cars. The Nissan lost the race......   If we were only racing dynos and wind tunnels and computers be much better off. 

Love it.

So the 240SX is getting replaced,    Is it ?

[jacksoni]

Scott- The base engine is based on- think- a ZR800 Arctic cat sled engine. Bore and stroke are 81x76 for just under 400cc/. The pipes were built per my engine guys specs ( more power would be available if were a drag sled both in tune and pipe design but he felt would not live 5 miles) with the idea that I needed a broader power curve, since as Rex points out, and I looked, there is no such thing as a really close ratio (that you can pick) that is affordable,  multispeed transmission. He kept saying I needed a 6 or 7 speed, and I kept saying there is no such animal. Ok I found some sequential thing that might have been close but was nearly $20K. Not happening. I do have a G Force 5 speed that has nearly unlimited ratios available and have them, especially the 4-5 shift, very close. Power range is close to 1000 rpm and that is about the drop in that last gear. Press together 5 cyl 30+" long crank........

Anyway, if I knew how to tune it and stopped messing with the tune I'd be better off. Last year my data logger worked on one run. Then there was the odd driver screw up forgetting to turn it on. etc

So am freshening the engine and we spent lot of time in wind tunnel last week with two cars. The Nissan lost the race......   If we were only racing dynos and wind tunnels and computers be much better off. 

Love it.

So the 240SX is getting replaced,    Is it ?

Well, yes. Long story, short version. After quitting Bonneville in 1996 after blown engine with fire at 260 or so, gave it a rest for few years and then built a firebird, put the engine from streamliner in it but NA instead of blown and raced at Maxton for a few years. Parked it again for close to 10 and got the bug again and built a new motor that made lot more power. Went 170 with it, still G/GC and figured was about a good as could do. Sold it. Put the engine in a friends G/GMS in 2010 and then got the Nissan which supposedly had similar Cd and less frontal area than the 'Bird hoping to go faster. Worked through 2018 on that, including wind tunnel time. and with lot of work barely matched the 'Bird until 2018 when changed the transmission to get around a big flat spot in the power curve on the 4-5 shift (G Force with adjustable ratios). Went 176. New record. Lasted 1 day. By about 15mph. Enter Kiwis. See prior posts in this thread. I won't relate issues with them. Suffice to say we went in search of  more power, thus the 5 cyl. The subject of the Firebird came into discussion after 2021 SW. I talked to the guy I sold it to, who was going to go racing with it but it sat for 10+ years and is clear will never in his hands. I "rented" it from him and took it and the Nissan to wind tunnel for direct comparison. 'Bird won. I have lot work to put it back into race shape and swap all systems into it. Will see. Am not sure I can match the exact wind tunnel changes but got Cd numbers you won't believe........  See this thread: http://www.landracing.com/forum/index.php?topic=4423.0  Gary Eaker is why we have this car and he has seen it. We beat his aero numbers though Wind Tunnels are like dynos. No two will read exactly the same.

[Hot Rod Lincoln]

all systems into it. Will see. Am not sure I can match the exact wind tunnel changes but got Cd numbers you won't believe........  See this thread: http://www.landracing.com/forum/index.php?topic=4423.0  Gary Eaker is why we have this car and he has seen it. We beat his aero numbers though Wind Tunnels are like dynos. No two will read exactly the same.

Both are tools to be used to your advantage.

I'd love to do some aero work with dad's cars. ..

I just might believe your Cd numbers ... try me     

[Stainless1]

I remember that car... The intercooler using N20 was interesting...
Can't wait to see how it goes Jack... hope to see you in impound again. 

[jacksoni]

all systems into it. Will see. Am not sure I can match the exact wind tunnel changes but got Cd numbers you won't believe........  See this thread: http://www.landracing.com/forum/index.php?topic=4423.0  Gary Eaker is why we have this car and he has seen it. We beat his aero numbers though Wind Tunnels are like dynos. No two will read exactly the same.

Both are tools to be used to your advantage.

I'd love to do some aero work with dad's cars. ..

I just might believe your Cd numbers ... try me 

Absolutely agree on the dyno and tunnel are tools to be used. So many people don't seem to understand that and it becomes "mine is bigger than yours"; "that dyno is happy." ; "that dyno is off, I said my engine was going to make 500hp and it only made 490. Something wrong with the dyno" HUH? You get the drift.  We  decided to take both cars and do a back to back comparison which was eye opening. The F/GC thunderbird should do well. Having built an Iron Duke Pontiac engine and knowing the competition in midget racing etc with them and Esslinger and others, am sort of familiar with them.

[Stan Back]

We only used a dyno once (free!).  Didn't give a damn what the numbers were, just cared which engine set-ups produced the most output.  Spent 3 hours making small changes and then repeating them to verify the results.  They turned out to be where we thought they were and had long since not made any real changes ($$$).

https://www.youtube.com/watch?v=nNoVYDO8_xg&authuser=0

[Old-N-Slow]

Jack:  On gear ratios:  For maybe 6 years, I ran a TZ700 sleeved down to 500cc.  That bike was the epitome of a peaky power curve.  In those six years, I NEVER got two back-to-back runs at peak RPM with optimum gearing.  The power band was just too narrow.

I just decided that if I had a slight (2-3 mph) tail wind, I could run my best speed.  If the tail wind turned into a head wind for return runs, I just left it in 5th gear, and hoped for the best.

I your case, if there is not an optimum set of ratios available for high and next-to-high, you could think about, say, 4th and 5th if they are closer. Just need a faster push off.

[jl222]

all systems into it. Will see. Am not sure I can match the exact wind tunnel changes but got Cd numbers you won't believe........  See this thread: http://www.landracing.com/forum/index.php?topic=4423.0  Gary Eaker is why we have this car and he has seen it. We beat his aero numbers though Wind Tunnels are like dynos. No two will read exactly the same.

Both are tools to be used to your advantage.

I'd love to do some aero work with dad's cars. ..

I just might believe your Cd numbers ... try me 

 Dad from Santa Barbara?

[Hot Rod Lincoln]

I don't remember the exact model but the car is a Nissan coupe. Which I thought was not imported to US but am not sure.  The engine is a Synergy V8 built in NZ. http://www.synergypower.co.nz/ 

Those engines are awesome .... but $55k .... Wow.

the 2400 cc engine  at 3 hp per cubic inch ... NICE

[jacksoni]

all systems into it. Will see. Am not sure I can match the exact wind tunnel changes but got Cd numbers you won't believe........  See this thread: http://www.landracing.com/forum/index.php?topic=4423.0  Gary Eaker is why we have this car and he has seen it. We beat his aero numbers though Wind Tunnels are like dynos. No two will read exactly the same.

Both are tools to be used to your advantage.

I'd love to do some aero work with dad's cars. ..

I just might believe your Cd numbers ... try me 

I sort of missed your last line there, or maybe ignored it. I was looking for something else and ran across this thread again. You have to recall that Drag= .00256V^2*Cd*A.( at std temp and pressure)Drag is what a tunnel measures. If the A entered is not accurate, say too high, the Cd will be low and vice versa. I don't know what Gary Eaker used but I measured my car as best I could in it's more or less stock ride and shape. If my area number is wrong then Cd is as well, inversely as above. With that we equaled what he got Cd-.235+ or-. In legal /GC configuration. Then we pushed things and added parts for /ALT. The very best we got was Cd=.191. Not telling what we did, LOL. Am behind schedule......... big surprise there.