What someone needs to do is create TPI intake that has the standard runners as we know them, but port the base to it's limit, from the las downward bend to the flange (last 1.5" or so or runner). Then punch a hole in the top of the runner at the bend and a corresponding hole in the floor of the plenum. Now install a rectangular runner between the base and plenum, and a pivot shaft running lengthwise through the base with a brass "flapper/damper door" that seals off the base/runner ceiling, or the "short cut" runner floor. Connect that shaft to an RPM activated controller, and have the thing switch from the standard "TPI" runner, to the "shortcut" runner at, say, 35-3800 RPM or so?

Voila! A cool looking, dual mode, extended range C4 intake.

 

GM did, it was called the zr1, they may have also threw in 4 valives for added fun, but that is a different story.

 

No they didn't. The ZR-1's two runners per cylinder are about the same length and are what I'd call a "mid length" runner(s).

 

Imagine this intake, the sheet plenum floor is the floor of a standard TPI intake. But cut the runner mouths flush with the plenum floor, retain the base runners and bolt on and install a valve in the base to switch runners.

 

I was trying to be funny, the runner lengths are the same as you stated but it uses an extra throttle valve per runner and extra injectors per runner that that are turned on and off when max performance is desired. (On the secondary runners)

 

GreggPenn I do not hate the Mini Ram.For ease of installation and top horsepower It is Great.You mentioned the article Ten Times the torque.It is one of my favorites.There is where you can see what the trade offs are for alot of commenly used intakes.In the article you will see the Mini Ram gets 45 more horsepower Than TPI but gives up 60 FT. LBS.of tourque.

 

^That is true. So the question becomes; if you have a 383 or 400 etc...how important is that tq that you'll lose? If all the tq is going to do is spin tire, and then hit a HP/RPM ceiling...then it's a good trade. If losing that tq is going to cause difficulties launching, OR diminished "driving experience", then it may not be a good trade. I'd submit that any 383+ engine that is decently built will have more than enough low-mid tq for driving experience and good launch, regardless of intake.


Copy. Sorry I didn't pick up on that.

 

I didn't mention gears in this thread,because it will not change the performance too much if the vette has 3.07 up 4.10. Vic proved the to me with his setup in his vette when we was Racing at Etown CC. I believe a vette will benefit for a TQ convertor then with gears. (3300 lbs avg. wt) Vic can tell you how I tried all kinds of intakes and cams in my sbc, when racing in the CC. My main goal was to keep the vette as an everyday street driver. I even had a 9" rear in the car at one time.

The SBC is a great engine, but all the work I did for the LS conversion was and is worth the time. Now back to the original topic, Miniram vs TPI.

Randy

 

This is where people's fundamental misunderstanding of power and torque comes into play (including in that otherwise excellent article!). I'm assuming you're comparing the Mini Ram to the TPIS Big Mouth intake in that article? So the Big Mouth intake made 60lb/ft more peak torque. So what? How much faster does that make the car?

The fact is that a torque rating at the crankshaft is irrelevant to predicting a car's performance. Power is what determines how fast a car accelerates. Period. There's no "yeah, but torque" statement to be made here. The car that can put down 45hp more will win...every...single...time. This is true both mathematically and in the real world.

It is true that if the car with higher peak power had a very narrow powerband and couldn't average a greater power output as it ran through its gears, then the lower-power car with a much broader power curve could equal it by outputting an equal amount of average power. It's also true that an engine with a peaky torque curve can feel less drivable and can be harder to keep in the fat part of its powerband.

But that's not the case in comparisons of these two intakes. In fact, the Mini Ram has a much, much broader and flatter torque curve and can average WAY more power under its curve. The Big Mouth test shows that it makes 80% of its peak torque from 2800-5500rpm, for a 2700rpm "useful" torque curve. Whereas the Mini Ram made 80% or more of its peak torque for all of the tested rpm and then some: at least a 3700rpm spread, and even more in reality.

In fact, the Mini Ram version will be the far easier car to drive in any spirited way. There will be lots of places where the driver would have to use an extra upshift and downshift with the Big Mouth version just because its torque curve is so narrow. Again, I have direct experience with this, having autocrossed a 5sp Camaro with the 305/TPI. There were lots of places were I needed to use 3rd gear, whereas an LT1 car could merrily keep accelerating in 2nd gear. The same advantage holds true if one is towing, or just tooling around the street.

The only caveat I have about the engine and graphs in that test is that the engine with the Mini Ram needed another 500rpm of safe rev range to fully take advantage of the power it was making. If 6000rpm is a structurally-induced redline, I would want to build that motor to go a little higher so it would be even more flexible and useful (and faster). Or perhaps on the flip side, I would consider juggling cam specs or cam timing to move everything 300-400rpm lower.*

But aside from that caveat, it's far and away the better engine combination. It will be way faster and easier and more pleasant to drive. Anyone would be foolish not to choose it if cost were not an issue. Back to the OP's original question, it's difficult to say whether it's "worth it" or not to spend the extra money if he already has the TPI intake. Notably, I didn't infer his intake was the Big Mouth that did the best in this cited test. So the difference between his intake and Mini Ram might actually be even greater. And there are real implications for cam selection depending on which intake one goes with.

*ETA: Looking at the cam sidebar in that article, they talked about using a "less wild" cam for TPI setups. I don't completely agree, because a restrictive intake like that can probably benefit from a fair amount of duration on intake. But whereas their cam had a 110* LCA, I would consider 112 or even 114 for a TPI engine, just to spread the torque curve a little wider. Conversely, for the Mini Ram setup I would go to 108* LCA for starters. I'd also try to get more lift from less duration (i.e., more radical ramp rates). And that engine with the Mini Ram would definitely tolerate and enjoy a compression ratio in the range of 11:1. All in all, I think their engine selection was at least an equal compromise, if not actually handicapping the Mini Ram setup more than the TPI.

 

A few years back I had built a
.030 over 350 ( 355)Sbc 1988 factory roller block
Dart 180 Iron Eagles Heads mild porting 72cc
Piston Speedpro .100 dome (70 LT1 piston) approx. 10:1 w/ head
Cams comp 282, GM HOT CAM and GM 847
intakes TPI, LT1 Conversion S/R and Dart Cool Can intake w/worked 750 carb

The engine was built for a S-10 to bracket race. I wanted to drive it to the track. Comp 282 and carb 12.2s on this setup

I went to Etown and seen they had a Corvette Challenge, and that's when the black hole began. Brought a 86 vette and stuck the sbc in, and change the cam to the Hot Cam with the TPI. The car 60ft 1.60s but only ran 13.6s. I change the intake to the LT1 conversion intake, the car pickup .5 and 5 mph.

I played with the different combos. I had the Hot Cam and the S/R with 3'' exhaust, 3.70 gears 3200 stall car ran 12.1s @ 112 mph. I took it to a dyno, it dyno 320 rwhp. That was about the same hp that it dyno when I had the engine in my S-10.

Two weeks later I put the Gm 847 cam and Lt1 intake on it and ran 11.6s @ 116 mph but I hated driving the car around. It was NOT fun to drive.

That's when the LS came. I put a lot of money and time in my C4 that I could had purchased a C6, be I enjoy driving and working on my C4

Randy

 

The MR made 95 more HP then the stock L98. I dont know why this debate is even a debate?

My 421 build made 520 hp and 560 tq at the crank with a miniram and small 195 AFR heads. The tq curve was like a table top and it had tq everywhere and the car was very quick. That same motor with a TPI intake would have made around 75 less hp and it wouldnt have been fast.

Numerous of guys over the years have installed miniram intakes on combo's from 350 cubes all the way to 450 cubes and the cars have performed. The key to this intake is a good tune like anything.

I forget the forum members name now but he had a 406 with a ported TPI and went to a miniram. His track times went down almost a full second and he pickec up 7 mph.

The intake is for a 305!!! If you want a fast car then its not the way to go. If you are happy to keep us with new 4 door sedans making 285 hp then keep the long runner intake on.

Too each there own but i didnt like owning a slow Corvette. Whether you have a stroker with a TPI intake or a bone stock car...The TPI is just boring and so is the power that it makes.

 

What do u think?

 

Well to be fair to Gregg's efforts here of the 2 intakes a bolt on MR would be much better choice for the H/C the OP is using. IMHO the TPI even in modified form would become just to peaky with that tight LSA cam. It would be a monster at 4000 RPM but weak somewhere above 5000rpm.
For that cam better choice would be a Super Ram (if one can be found) or a Holley Stealth Ram (but no EGR for smog legal cars).

Don't know what happened to Davis here but I expect he should make an informed choice now.





Matthew I have to say something here as you keep comparing HP and torque at different RPM peaks. HP is just a mathematical relationship of torque at an certain RPM which gives it a function of time. You can't compare peak torque at one RPM to peak HP at another RPM. Higher torque means higher HP at the same RPM and that's a fact. Now your comparing power over the entire power band to another and yes a higher peak torque motor/combo can easily make less peak HP than another motor/combo and the power under the curve can be less also.
But it's also possible for the higher peak torque motor/combo to make more power under the curve. Cam specs, stroke, c.i. even compression ratio affect this so we can't blame this on just the intake design.





Looks pretty bad azz. But it's another Ram intake. Super Ram, Stealth Ram, Tunnel Ram, sheet metal intake are all tuning for a certain power band. That one does have some refinements. But improvements for performance never end. How much can one afford?

 

Yep. I wasn't propositioning THAT intake...just showing how the runners had been "merged" with a TPI base. IF you did the same, but left the TPI base's runners intact, installed a valve, and stuffed those (shortened) runners into the floor of the TPI plenum...then you'd have your "TPI towak monstah" at 3200 RPM then switch to a short/mid-length runner intake (like a Pro-Flow) at an RPM of your choice. Retain the looks of TPI, but have your cake (high RPM tq) too.

 

The reason it is a debate largely has to do with the satisfaction/perception of one person vs another. You say a 421 with 450hp (which would be your old car "saddled" with a TPI) wouldn't be fun/fast. I would argue most forum readers/members would be thrilled to have that combo.

I don't know what traffic/roads are like where you live but they might be less densely traveled than some of the major cities of the readers.

What any person chooses to do (spend) on a car may be more than the limit of their cash reserves. That's a big part of why there's a debate. Theoretical talk that proves HP is always better than the torque it's a function of is nice. (BTW, I'd like to see the reason Challenges cars were so good compared to their competition debated as mechanical theory.) But, I'd also like to hear when/where/why someone with a 400-500rwhp car is sure they NEEDED that power in a street situation.

I was the only one that described why my setup seems fast enough for what I do. Sometimes a perspective builder wants to visualize what a combo would do on the street. I don't think you did that.

I'm sure your old car was faster than mine but that doesn't mean anything/everything else is not "fast". My "winter" vehicle is a 230hp 4WD that weighs 4000 lbs and there's no way you can say the vette isn't way faster. FWIW, the Isuzu Vehicross was considered breakthrough in the 90's for SUV performance. In fact, they called it the first PUV (Performance Utility Vehicle). In the Vehicross forum(s), you'll find people who insist THAT vehicle is "fast". And, compared to it's 4WD predecessors, it was fast. It won several events on the Baja circuit.

My effort in this thread was an attempt to bring practicality to the discussion. I also tried to quality what's faster...to avoid doubt in that regard. The reason for the debate is more complicated than that.

That said, I think the cam posted in the OP is better suited to a MR unless the OP's TPI is significantly shortened. But, his current intake might be "fast" enough to make it home with ice cream before it melts.

 

Oh boy, here we go again! Although we describe the power of an engine as a relationship between torque and rpm, it is not a function of that. Power is literally nothing more than the rate at which energy is transferred, in this case from the BTUs of gasoline to the crankshaft or driven wheels. It is completely possible to measure power without knowing "torque." It is also completely possible to accurately predict acceleration by know the power output of an engine along with dimensions of the car it's in. It is not possible to predict anything about a car's performance if you only know the torque. That, again, is fact. Power is the only meaningful engine spec in determining the speed or acceleration a car can attain. If everything else about a car is equal, then the one that can apply the most power will accelerate faster. It really is that simple.

That is only relevant if you're racing in some strange class that limits rpm of the engine. IndyCar comes to mind here: I think they are capped at 12krpm, and therefore they obviously have to focus on building in higher cylinder pressures (ergo "torque") within that limit. But if that were not a rule, they would focus on higher rpm every time. The best illustration of this was the 20krpm days of F1 when displacement and natural aspiration were the only limits. Nobody built "torque motors" for that rule set! That would have been stupid, and the results would have shown that. My car has a ported stock LT4 intake (more or less a Mini Ram). If someone in an L98 car wants to race me but says I have to shift at 4500rpm, I think I'll pass. Because that would be as silly as it sounds.

Sure it is, if that peak is higher enough and still at a high enough rpm. For example, if one engine makes 200lb/ft at 8000rpm and another makes 500lb/ft at 4000rpm, then the latter engine will be the faster engine. Not because it makes more torque, but because it makes more power. If it makes more power, it makes more power. Again, it really is that simple.

Can't blame what? The referenced article made it pretty clear that the intakes were the only things changed. The 50-100hp differences were 100% due to the different intakes. As I noted before, I think their cam selection may have impaired the Mini Ram setup even more than the TBI setups.

Gregg, I know what you're trying to say here. But the fact is that a if the OP is going through the expense and trouble of building a stroker motor for his C4, including an aftermarket cam, then the MR intake is going to not only be way faster but also be a far nicer street motor. It's a better street motor because it's way more flexible. It will be faster because it will have a lot more power. I don't know which of those priorities is highest for the OP (I can guess!), but since he can have his cake and eat it too then the MR is the only logical choice, if it's within his budget. If it were me, I'd buy a MR and sell my ported TPI intake to someone who thinks peak torque is really important. There's a sucker born every minute.

Regarding the Challenge cars, I'm assuming you are referring the C4's success in the actual Escort WC series? I actually got to watch them race at Texas World Speedway, at the point where the Lotus Esprits were the only real competition they had. By this point, the series was also piling on the ballast to the C4s to try to equalize the competition. The simple fact is that, no matter how much magazines wanted to sell us on the virtues of exotic cars like Lotuses and Ferrari 328s, the C4 was the fastest and most power sports car in its day, short of maybe the unobtainable supercars like the Testa Rossa and 959. The Corvettes simply made a lot more actual power than a 2.2L Lotus, notwithstanding the turbo on the Lotus. They also handled better and had a lot more grip. This was always the difference between magazine racing and real racing. The C4 was, very simply, the best obtainable sports car of its time, in every way except quality (but the Lotus was even worse on quality!). That showed on the track.

It's probably also worth pointing out that it would have been trivially easy to cheat on L98 power, even with the TPI limitations. Some about of porting could be disguised. Cheater cams with the same max lift and duration but way faster ramps could be used, which would measure the same but provide more power. Intakes could be siamesed, etc. With literally decades of NASCAR cheating experience in the knowledge base, there's probably never been a better base for cheating! I'm sure that as the Esprits used more and more boost (as I'm sure they tried) and the ballast disparity kept growing, the C4 teams worked on proven cheat techniques.

 

Not b/c of TPI. It was better because of other features that mattered more; max lateral grip, transient stability, braking, ability to inspire confidence...and more accurately, because everything else sucked! What was going to beat a C4? A Datsun 300ZX? No. Mitsubushi, Starion? No. A 4 cylinder Porsche 944? No. An '80's Audi?? A Toyota Celica/Supra? Izusu Impluse?? I mean...look at the garbage that was on track with the 'Vette in the mid '80's. The 'Vette most certainly didn't dominate b/c of TPI, if that's what you're implying. The engine certainly didn't hurt; it did have more hp than most sporty cars of the era...but if you'd have slapped a mid length or short runner intake on a challenge car...it would have won even more.

EDIT: Just saw that Mathew covered it pretty well, already.

 

Heh, well just to pile on: if they had been able to use LT1 engines in those days, the bloodbath would have just been worse! And I'm sure the C4 drivers would have been a lot more happy.

 

To the topic of "width of powerband", let me post this:

With the ZF6 and my limited powerband....

1st gets me to ~40mph with it's "narrow power band"
2nd covers 20-55mph
3rd covers 35-80mph

For anything short of a complete stop, 2nd gear covers anything I'd want to do in town. And, I'd average 400rwtq throughout that "short burst". I don't think it takes much more than around 2 seconds....maybe 3 tops.

3rd covers highway speeds from the minimum to the maximum with the same average torque. It takes a bit longer in 3rd...maybe 3-4 seconds?

If I had a 6k rpm intake, 2nd would cover all the way to 70+mph
If I had a 6k rpm intake, 3rd would cover all the way to 105+mph

On the hwy, I'm not sure it would help. At 55-60, I'm not sure I'd be inclined to shift "around the horn" from 4th to 2nd. 5th to 2nd, maybe but matching rpms would be a bit more challenge. Yes, I'd catch at bit more power due to the gearing.

In the city, blasting past 55mph to 70mph makes no sense. In fact, 55mph is illegal in most city situations. That's why I'm saying the "limited" powerband of a TPI doesn't compromise a streetcar much at all.

I hope this helps make is clear why I posted that a good, large TPI on a 383 isn't a bad option for a ZF6 (street-driven) car. Again, I like the shorter runner intakes if you're running an automatic BOTH for the downshifts AND the D36 limitations. For the auto, less torque and a wider powerband DOES make the most sense.

I hope you can also see why I don't miss (or need) the ability to drop two gears to have a fun (and what I'd call) fast car. Having an average of 400 ft/lbs of torque in a short (35-40mph) powerband really does cover normal driving "needs".

Finally, I do understand why a wider powerband and/or lower gearing delivers more power to the ground. And, I'm not trying to say the TPI is a faster quarter mile intake. If I made sense, you might be able to see why having that "monster narrow" powerband isn't such a bad thing for practical application. It only makes sense IF you understand what "narrow" really means...and it's not THAT narrow for city/hwy driving.

 

I should also add that having maximum TORQUE from 20-55mph (city) with the same thing from 35-80 (hwy) isn't such a bad thing (compared to shifting to get maximum HP in a wider powerband. I think this was obvious in my prior post but I wanted to state it.



------------------------------------------------------------




FWIW, if you are interested why I've hesitated in converting to a higher rpm intake, you can read about it in my thread just posted on Speedtalk.

It's not clear if I have a RA "balance issue" that makes it safer to stick to a lower shift point. (It's the "issue" I eluded to on page 1 of this thread.) I think what I did was such an unusual combination of parts that it might not be in many builder's "wheelhouse" (or general knowledge). I'm not convinced I'll find a good answer at Speedtalk -- let alone here. But, as with other aspects of this hobby, I like to second-guess my decisions. LOL

This isn't meant as a negative comment -- just what I realistically feel I'm apt to gain from building an unsual, unplanned, and less-than-ideal combo.

One final comment I'd like to make to people looking for advice on builders....Most (if not all) people encouraged me to take the advice on the builder I chose....and to trust his knowledge. Combined with my unwillingness to ship everything to a builder and/or wait an extra year for the local "expert" to do the build, that's the OTHER reason I decided to trust my builder. If you read the Speedtalk thread, you will understand this comment!!!

As was posted in my Speedtalk thread, there are more reasons to consider a forged crank that the rwhp of the build. I think it's a valuable lesson for this forum -- even if my build turns out to be fundamentally sound.