Ok so i saw shifty posted in a thread the thing that really holds us back(96-98s)areIMRC's and the long runner intake, so how do you fix this? simply take off the IMRC? and just throw a hacksaw at the intake? lol i sure hope not, but yeah looking for suggestions, im not horrible when it comes to working on my own stuff so i don't think this would be much of a problem, just don't know where to start and how to do it so let me knowwwwwww.

Thanks

edit: oh yeah would either of these things cause me to throw a code? i got emssions in oct.

 

People seem to get different results. The consensus from people who have done it seems to be that you will lose some low end torque if you get rid of the the IMRC butterflies, but you will pick up top end power. If you have steep gears (4.30:1), you probably won't even notice the torque loss. They are there because our heads have way too much intake port volume for the size of the engine. Too much volume == low air velocity, which prevents the air from filling the cylinders efficiently when the valves are open. In other words, low volumetric efficiency. By closing off one of the intake ports at low engine speeds, the velocity of the air column is increased because it has a smaller cross sectional area to accomodate the flow. This gives the air column velocity (and momentum) thus allowing it to more effectively fill the cylinder. At high engine speeds (>3200 rpm), this isn't a problem, which is why the butterflies open above that speed.

This mod works best for a high-revving N/A engine, or in forced induction applications where something is pushing the air into the cylinder under pressure. You also will need to turn the IMRC controller off in your tune (or rig it up so the computer still thinks it's attached) or you will throw a code. The heads have lots of high RPM potential, but you will need to build the rest of the engine to realize that potential.

From what I've read about the process of shortening the intake manifold runners, people somehow take the intake runners out, cut them to the desired length, and epoxy them back in place. Dunno exactly how they get them out though. Some kind of solvent maybe?

 

there is no way i woulda have(nor do i know that ****) been able to write it like that... But yes, i guess i kinda forgot that, if you were to do it, you would need steeper gears to kind of make up for the loss and already lack of low end tq, but 4.10s would do fine..
hell, anything is better then stock gears(sad to say i have yet to switch my gears[sm=chairshot.gif], but i will eventually be going with 3.90s for road racing).

Let me get you some more information on this.


Edit: You might want to check your PMs.. youve got mail! lol

 

I did IMRC delete's last year and dyno'd before and after. I saw 4rwhp loss from 1800-2200rpms and a mere 6rwtq loss and then after that it was even and up top was a little bit more hp. (3rwhp to be exact)
It's not much of a dyno difference as it was seat of the pants. I could def tell it lagged a bit and was surprised it was only so little loss.
The Intake runner shortening I would only reccomend for roots/twin screw s/c'ers as they have low end grunt almost instantly since boost is right there. That's the only aplication I believe you would benefit from a shortened runner intake. I have a centrifugal on my car now and it would not be wise for me to shorten the runners because my car doesn't get into boost until 3500+rpms which would make me mega lag at low rpms. Don't get me wrong, I still have more than 300rwtq at 2200rpms but it's not comparable to the loss that would be for a lack of other words...achieved.
IMRC delete will set of a check engine light because the module has a signal feed going into the module to turn it on and then sends out a signal to the ecu to confirm because timing advancement plays a big role whether or not they open and close!

 

You are wrong for the application for the short runner intake. I sent him many links that proved otherwise. There have been 96-98 cobra owners who have picked up 30rwhp and like 26rwtq from doing a short runner and IMRC deletes. You just have to know what you are doing, and get it done correctly. You can also change the runners on the intake according to what gears you will have in the car.

And yes, you would see a gain, and a mere loss of maybe 6tq if you did a shortrunner, and either way, you have a centrifigual SC.. You should have 4.10-4.30 gears man. And gears alone would solve the problem of that small loss of TQ


Also its good to delete the IMRCs because after some time, they get stuck.

 

I'm doing an IMRC delete at this very moment as part of my twin turbo installation. The shop was putting J-B weld in the IMRC plate holes just this morning while I was there. Not to steal this thread, but I would be interested to know if shortened runners would help out even though I'm not planning on changing my engine's operating range (still using stock camshafts).

 

J-B Weld ftmfw!

 

What are you talking about??? I was talking about 6rwtq loss with the IMRC Delete's, not the shortrunner. The shortrunner can give some good gains, but with a stock N/A application, it's not going to be that helpful. You need some other internal work to make the shortrunner useful without a s/c'er.

 

.. yes you might lose a wopping 3rwtq from deleting the IMRCs, but the benefit from it is worth it later, and if you have steeper gears, it makes up for it.....a shortrunner IS beneficial on an N/A engine, you do not need other internal work to make it benficial to our cars. Yes if one slaps on a SCer, it will obviously become even more benficial, but that is true with ANY modification to the engine and FI.

 

Here's the lowdown on runner lengths:

Stock: good for n/a cars with 3.27-3.73 gears and stock shortblocks and centri charged motors staying under 7k. The centri charged combos benefit from stock runner length because they normally run stock -3.73 gears. The intake should be "cleaned up" to get max power.

Staggered lengths: I've been toying with the idea of cutting every other runner in the firing order in hopes of producing an intake that will give a broader hp/tq curve for cars with 3.27-3.73 gears. The intake would have four stock length runners and four that are shortened 1.5". The only problem is that the distance from the runner inlet to the plenum floor will not be consistent and I'm not sure how that'll affect power but there's only one way to find out.

Shortened 1.5":n/a; 4.10 or steeper gears aren't required but are highly recommended. Low end losses can be recovered by tuning but most tuners will not advance the timing enough to get the power below 4k back to the stock intake levels. Peak power rpm will be raised about 300rpm and the drop off after peak power is drastically reduced. Good for stock and cammed motors operating under 7500rpm.
Centri charged cars with 4.10s or steeper or those seeing more than 7k will benefit from a shorter runner but no more than 1.5". A high number of centri charged motors have lost power with the very short runners...stay away from them unless you are turning upwards of 8500rpm. It's not uncommon to get peak gains of 15-20rwhp and up to 30rwhp after peak on a stock longblock motor.

2" shortened runners: I've made a couple of these for n/a and turbo motors and the results have been great. The intake I made for my car and later sold to davidj5491 had the runners shortened 2" (1 and 8 were shortened 2.5") and the plenum floor raised 2" worked great. Torque losses were minimal on my motor and I picked up over 20rwhp at peak and 30rwhp at 7k. davidj5491 actually picked up some power down low...dunno why, maybe it was his stock cams. I'd like to do some testing to see how the plenum affecting power but that will have to wait till someone adds more hours to the day.

A 2" runner will also work great with a turbochargers also since the turbo motors get on boost much quicker than a centri charged engine. A Modular Fords member has one of my 2" cut/raised plenum floor intakes and there should be some numbers coming soon (twin turbo).

SHM style, very short runners: Aren't good for any motor. In fact, John Mihiovetz's recently replaced his "very short" runner intake with a custom intake with longer runners and made more power/torque...his motor spins over 9k. So, stay away from any intakes with very short runners.

Of course opinions differ as do combinations and results. One factor that can not be overlooked is the quality/aggressiveness of the person doing the tune. They play a great role in the results/gains you'll achieve from any short runner and most of the "Great" results you here are from those tuners that aren't afraid to be aggressive. So, if you or your tuner aren't willing to be aggressive, don't waste your money on a short runner cause you'll be dissappointed with the results.