just back from the track, ran 11.45et @ 115mph, this was with carbs jetted up 2 sizes on four corners, water injection at 1000cc p/min up from 800cc p/min and timing at 18degs up from 15degs, this surprised me because #1 cyl was down to 60psi after first run, this was due to the damage when water pump motor failed last weekend and engine over heated and blew rad hose went the head gasket failed. the car was running strong, even with 1 cyl down, so i tried the 1to1 drive pulley and the boost went from 5psi to 15psi, needless to say the head gasket is out again.but i think i have a comb i can live with on pump gas and water injection, i just need to build a fresh engine over the winter, this poor baby has been cooked enough, with 10% under and the timing and injection set this should run low 11`s, the 60ft`s were at 1.57et`s, i wish i had some video. http://family.webshots.com/photo/248344 ... ost=family http://family.webshots.com/photo/295462 ... ost=family http://family.webshots.com/photo/295462 ... ost=family

I wish you had some video too! Please get some next time!

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-1972 Valiant-

'72 Valiant

Sounds like great progress, Terry. 10s on pump gas, maybe???

Lou

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Home of Slant6-powered fun machines since 1988

with the strong 1.50 60ft, and the mid 11.4`s to 11.6`s with all this engine had going against it, #1 cyl was just about dead and all the others still had the top rings with no tension left from over heating and seeing all the abuse i have given her last weekend and this one, just to stay in the 11`s suprised me.the 15psi with the 1/1 drive was nuts , i never thought she would build that kind of boost, if i had i wouldn`t have tried it. i know it`s going to be a interesting season next year and a busy winter, i suppose i am lucky owers are so long.

Good job Terry!

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Official Cookie and Mater Tormentor.

Was that a steel shim that failed? You might still be experiencing some low level knock. I know there was an overheating issue last week. Get a wide band for the new engine. You will be amazed.

there maybe, i haven`t taken it apart yet, but everything was working will untill i hit 15psi with the 1/1 pulley on, i didn`t back off the timing because i didn`t dream of hitting 15psi with that pulley change. would there be any difference in the vol of intake charge between 15psi with a turbo and 15psi with a blower? or does the higher rotating speed of a turbo pump just as much air vol as a blower at lower speed?

I can't explain it all that well. 15psi does not necessarily equal 15psi. It gets into the efficiecy of the compressors/trim...ect...that's why there are so many different turbos to choose from for a particular application. I don't even know how to compare a superchargre and its pumping efficiency. We know it heats air but how much vs a turbo?

i suppose i will figue that out with time . i am working on getting the isky o-ring tool and when i have all the damage fixed i will have to invest in a wide band o2 reader.i hope my list is not to long i only have untill june and i was hoping to get the street car up and running this winter for the spring.

The difference isn't on the intake side, its on the exhaust side. When a turbo delivers you 15 PSI on the intake side, its inducing MORE than 15 psi of back-pressure on the exhaust side to do it. With a blower, there is no increase in back-pressure as the boost builds, so the volume flow through the engine is indeed higher for, say, 15 psi on the blower versus 15 psi on the turbo. You still pay the piper because the blower saps power from the crankshaft instead of sapping it by raising back pressure, but the flow characteristics are definitely different, so you may find that you lean out and/or need more water injection for a blower at 15 psi than a turbo at 15 psi because of the way breathing is affected.

That probably doesn't make as much sense as it should. Nutshell: turbo => exhaust back pressure rises with boost pressure, blower => exhaust back pressure independent of boost pressure.

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Corky Bell feels that street turbos should run on the order of twice as much exhaust pressure as intake manifold pressure. If the turbine inlet pressure (TIP) to manifold pressure ratio is greater than 2:1 the turbo is too small and is choking the system. Less than 2:1 and response suffers. It's really easy to put a tiny turbo on an engine and get big boost numbers, but because the TIP is so high the mass flow thought the engine and the resulting power is relatively low. This also puts a lot of heat into the engine. Early turbo Porsches had relatively large turbochargers so that the exhaust back pressure was lower and the turbo compressor was efficient at higher speeds so the heat load on the engine was lower. Of course low speed boost response was poor, but it pretty much had to be so to keep the air cooled engine from melting down.

Many real race cars though run less turbine inlet pressure than manifold pressure. TIP to manifold pressure ratio <1:1. As the TIP to manifold pressure ratio falls power increases.

Also, turbo compressors are much more efficient than a Roots blower. Turbo compressors therefore heat the intake charge much less. Intercooling reduces the inlet temperature further. A turbocharged and intercooled engine should make more power running the same boost pressure as a Roots blown engine if no serious design mistakes are made.

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Joshua

thanks it give you some things to think about, for what i want 5 to7 psi will be lots, if i can get mid to low 11`s et the car will make super pro class, which is 11.49et and quicker, i have a trophy for street class with my slantsix street car, 13.49et`s and slower, a trophy for pro class with this car 11.49et`s and slower, if i can make this a consistent 11`s car so i can concentrate on the tree i will get my goal of winning with the big boys.

i was searching slant six stuff on youtube, and I came across your video. Your engine, is the most badass engine i think i have ever seen.

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What's that fuzzy blue thing being hurled this way?
::stick::
BOOSH!!!

I've heard that claim, and I believe it is basically true, but I wonder if the difference is really significant. The vast majority of the heating of the intake air through either type compressor *should* be due to the compression itself. A Roots adds some small amount of additional heat because of leakage past the rotor tips turbulating the air and then re-ingesting the turbulent air, and a turbo adds some small amount of additional heat through conduction from the red-hot turbine sitting right next to the compressor. How much real-world difference is there if you could eliminate all other factors? I don't really know.

Again, I agree when it comes to crankshaft output power at the peak of the power curve. But the way the engine responds across the power band may be completely different, the cam profile that works best may be different, etc. for the two. A mechanically blown engine (whether its a roots, Paxton, or screw-type blower) is working with a lot less back-pressure at the exhaust valves (essentially just atmospheric pressure plus any back pressure due to mufflers, catalysts, and exhaust plumbing) and that's going to change the scavenging characteristics relative to a turbo engine. And of course you can intercool a mechanically blown system just like a turbo system, too.

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i haven`t found any video yet but i have some new pitures on webshots