I agree that the miniram looks like a good idea ,at first.
Ive run all 4 common intakes
ported tpi
super ram
mini ram
stealth ram
the ported tpi gained me about 20hp over the stock TPI.(power range, 1500-4500rpm
super ram gained me about 45hp over the stock TPI(power range 2000-5500rpm)
the mini ram ram gained me about 55hp over the stock TPI but lost torque below 5000rpm(power range about 5500-7500rpm) and that power was over a very narrow range
the stealth ram gained me about 68 average hp and close to 90hp at peak but lost torque below 4000rpm compared to the stock TPI intake (power range about 4000-6800rpm)
now keep in mind Ive got a full roller 383 11:1cpr with ported trickflow heads and full length headers, the stock TPI totally strangles that engines airflow above 4500rpm, so any intake system that flows more air lets the engine breath and produce better hp, the steath ram and the other intakes require a cam and headers to effectively use the better airflowI was asked?"will the steath ram flow enough air to make max power"
well lets do the math,
the steath ram is designed for the sbc engine, the largest normally built sbc displacement is the 434cid engine. the 434 engine spinning 7000rpm (thats well over the normall rpm for that engine even in race form) can use about 880cfm at 100% efficiency. the steath ram is cut to fit a 58-60mm twin throttle body bore size. that bore size flows about 1000cfm, well above the level thats necessary to feed even that larger than normal displacement.
now holley says that the ports in the steath ram flow about 300cfm
and several people have flowed the intake and thats true, but keep in mind that flow benches measure steady state flow, also keep in mind that the 4 cycle engine has a total of 720 degs in the total repetitive cycle and only about 250 (THE CAMS INTAKE DURRATION) of those 720 degrees are used to flow air into the cylinders on the intake stroke and if you carefully take the time to measure youll find that about 85% of that 250 degrees is flowing a usefull amount of airflow for a total of about 259cfm at a time per cycle trying to move into a single cylinder. now since the cylinder on a 434 spinning 7000rpm only needs 110 cfm even at a steady state flow into the cylinder and the cylinder can only hold that aproximate 110cfm the intake (steath ram) flows more than enough air to make max power , and more than enough air to to feed the largest flowing heads that normally fit the steathrams intake ports (like the 195cc AFR cnc heads)
the manifold is exactly the correct size! remember that each runner is a column of air and that air has volume, weight and energy. now its true that the cylinder can only take 110cfm BUT remember that during of all the time the engine is running is in a 720 degree repetitive cycle? and the air can only flow into the cylinder durring the 250 degrees or so that the valve is held open by the cam? well that means that the air flow needed is 720 degs/250 degrees x 110=316cfm or just about what the intake port on the stealth ram can flow at max volume. or put another way youll need to push 316cfm down the port because its only open durring 34.7% of the time available to fill that cylinder
, its sized to meet the max flow potential thats likely to be needed but the LENGTH of the runners from the back of the intake valve to the plenum plus the effective size and length of the primary pipes on the headers, the engines cpr and displacement and the cam timeing determines the rpm range that efficient cylinder scavageing takes place, the TPI system has intake runners about 21" total in length and is effective in the 1500rpm-3500rpm range, the super ram has runners about 17" long makeing it effective in the 3000rpm-5000rpm range, the stealth ram has about 10" total runner length makeing it effective in the 4500rpm-6500rpm range (right were max power with most sbc engines is normally found) the mini rams shorter runners place its effective range partly above the rpm range a l98 engine will ever get into. look at it this way, the pressure waves that make a tuned intake work are moveing at a more or less set speed up and down the runners at any given rpm, the size of the runners effects this thats true but most of the intakes mentioned are similar in size as to the intake ports as the intakes match the chevy cylinder heads but the length, varies this makes the returning pressure waves and restrictions in the port vary with the length. here read this
http://www.grapeaperacing.com/Grape...kehelmholtz.cfm
http://www.engr.colostate.edu/~alla...ength/pipe.html
but keep in mind that the rpm ranges its discussing are a little higher than whats involved due to the port sizes, and that there are first, second, and third and fourth order reflective pressure waves effecting the ram tuneing the fourth order wave is whats normally used.heres what my computer says
Computation Results:
Input length is 10 inches
For 2nd harmonic, RPM range is from 9790 to 11880 with a pulse strength of 10 percent
For 3rd harmonic, RPM range is from 7356 to 8407 with a pulse strength of 7 percent
For 4th harmonic, RPM range is from 5735 to 6413 with a pulse strength of 4 percent
the first through third order waves normally would require an intake to large to fit under a cars hood, and keep in mind that prediction is for the PEAK effective level, not the total effective level
displacement has an effect but the efficiency of the exhaust scavageing and the intake runner length, compression ratio, cam timeing, etc also have an effect.
everything in an engine is a compromise, yet some designs are far better than others at effectively meeting the goals
I have not dynoed my engine yet but I did gain 6-6.5 tenths in the 1/4 mile swapping from the extremely restrictive TPI to the steath ram intake on my full roller, trickflow ported,11:1 cpr 383 with full length headers and DOUG over at HOLLEY gained 63hp swapping from a TPI to the steath ram on a STOCK camaro, BOTH THOSE RESULTS SHOW a 63hp(for HOLLEY) and a-90hp improvement for me with a average of 68hp improvement if the track times are an indicator and HOLLEY stopped way short of the 6500rpm durring their testing.that I run my 383 too durring a race, now the best IVE EVER seen on the TPI to LT1 swap was about 2 tenths and about 20hp, (Ill gladly post hp numbers when I get the engine dynoed) but for now the results are good enough to show a huge improvement on my engine, now Ill grant you that trying to run a 383 like that and trying to let it breath through a ported TPI was SERIOUSLY STRANGLEING that engine but none the less the steath ram did SERIOUSLY improve the power and Ill also grant you that the TPI can,t come close to supplying air to a almost full racing 383 turning 6500rpm and was never designed to do so! but the fact remains that the steath ram can and does flow far more air that the TPI and from what IVE seen flows at least as much air and makes more torque that the MINI-RAM intake which I also tested on my 383 (which is basically a large port LT1 intake in design) and which proved to make less torque and less power on my 383 and it (the mini-ram) made that lower power over a narrower rpm range (if you read my other post you know the mini-ram made about 55hp over the TPI on my 383, good but not as good as the steath ram)
look the formula for HP is (torque x rpm/5252=hp)
now if your tpi has a peak 400ft lbs of tq at 3500 rpm thats (3500 x 400/5252=266hp
now move that same 400ft lbs up just 1500rpm in the engines torque curve and 5000rpm x 400ft lbs/5252=380hp
thats a 114hp gain with no increase in engine torque just moving the torque curve further up in the rpm range
now not one person thats yet tried the steath ram has said anything but that the steath ram moves the torque range about 2000rpm higher in the engines rpm range and slightly lowers the torque , in fact a 63-90hp gain is before Ive learned to correctly tune the EFI and timeing curves, greater power is bound to be the result of further tuneing and the steath rams 45%-50% greater air flow potential over the TPI intake
while I agree the tpi had reached its peak hp at 4600rpm the steath ram power curve was still on its way up , HOLLEY stopped the test because of worries about damage to a totally stock camaro engine they did not own, look at the data again
HERES HOLLEYS TEST ON A STOCK 350 with just a steath ram replaceing the TPI INTAKE
RPM Stock HP Stealthram HP Diff
3400 190 175 -15
3600 200 188 -12
3800 209 198 -11
4000 210 204 -6
4200 212 210 -2
4400 213 223 +10
4600 214 234 +20
4800 210 240 +30
5000 198 239 +41
5100 184 238 +54
5200 174 237 +63
trust me bye 6000rpm the steath ram would have easily pulled much higher hp numbers but because Holley chose not to chance floating the valves they stopped the test way lower than the stealth rams peak hp numbers. the steath rams effective range is in the 4500-6500rpm range, the test results were stopped well short of the rpm ranges the steath ram would shine in. I will grant you that most totally stock engines are not run up to 6500rpm but then anyone installing a steath ram is not building a stock engine! and quite reasonably will install at least a cam. and headers and possiably a much better flowing set of cylinder heads if they understand the concept of increased airflow in and out of the cylinders to produce max hp. now you could also make those changes to a TPI equipted engine and see hp gains but the more you improve the rest of the engines ability to flow more air the bigger the restriction to that flow the TPI becomes and the greater your hp gains when you finely swap and remove that last restrictive part of the combo. you can add AFR heads a full roller cam, headers, ETC but keep the stock TPI and your still limited to about 200-210cfm per port, swap to the steath ram and your now up to at least 280cfm-300cfm like the heads flow with a good roller cam
potential hp from airflow is approximated with this formula
(max airflow x .257 x cylinders=hp) that means a stock TPI intake limits you to about 431hp the steath rams better flow raises the potential to about 600hp.
btw heres a cut away of the lt1 intake,(THE MINI RAM IS VERY SIMILAR) notice how short the ports are, this costs lots of low rpm torque
notice how the steath ram ports are more than twice as long to build more torque
now if your thinking port lenth and voluum don,t matter,your just flat out wrong about the port length and volume not effecting the engines torque curve, want proof! read these, and why do you think the TPI makes such great low rpm torque and swapping to the steath ram raised the rpm range 2000rpm,read these,
http://www.howstuffworks.com/question517.htm
http://www.newcovenant.com/speedcrafter/calculators/intake.htm
http://www.rbracing-rsr.com/runnertorquecalc.html
http://www.grapeaperacing.com/GrapeApeRacing/tech/intaketuned.cfm
http://victorylibrary.com/mopar/intake-tech-c.htm
http://www.grapeaperacing.com/GrapeApeRacing/tech/intakehelmholtz.cfm
http://www.rapidline.com/calc/engsim/pcesinta.htm
now I will agree that EFI is less impacted than carb intakes by port length and volume but less effected in no way equals not effected, years of tuning a dragster type engine running a stack injector tubes like these in my old vette
http://www.kinsler.com/images/man_4.jpg
has proven that changes in port length can move the torque curve higher and lower in the rpm range I had 4 sets of stacks from 6" to 18 inches long to adjust the torque curve on my old bbc race car
