i took my car down a shop here in winnipeg, canada(Jackson Autosport) to put a K&N filter on order recently. he asked to take a look at the car before going any further(which i thought was a classy move).

he recommended against doing anything other than replacing the filter in there due to the cold air intake being just as good(or near enough not to matter) as anything he could suggest otherwise. i took his advice(the direction i was leaning anyway) and put the filter on order.

on a whim i decided to take a closer look at the intake tonight. the intake chamber seemed efficient enough, appearing to draw air up from underneath the front of the car. this gets to the heart of my question.

i couldnt find any clear intake path from underneath the chamber under the hood. a cursory look at the intake area gives you the impression of a free flowing path for the air from the front end, under the hood up to the intake chamber. theres a plastic barrier that looks like it should have a use but it just blocks a clear path for any air flow from the front end. blocks it pretty good to.

im wondering if this is normal. is the intake designed to not have a direct influx of cool air? should i leave it the way it is or try to improve the air flow?

 

I'll have to take a look at that. I don't see why the crazy Japs would have intentionally blocked off any route for a cold air intake; but when you start thinking about it is it really worth all the effort to change it? If you had an airpipe coming straight from the front of the car for best air flow, then it would still have to make a hard right to enter the VDI. This would pretty much offset any gains from the increased volume and more cold air. I think the best way to set your intake up is with a cone filter that has a box built around it, maybe a hose running through the FTP lens (I saw one on here that looked pretty nice) that still allows the factory "snorkle" system to operate.

 

ironically it does have a an intake nozel in the front that leads off to the right and goes nowhere near the intake entrance. i have no idea what that could be for.

i was thinking of just taking out that piece blocking the intake and setting a piece of plastic to scoop air up from the spaces in the in the front end to funnel air strait into the chamber. i dont think that would be to difficult. might not be as good as a custom job, but its certainly cheaper and i can anticipate an improvement of some sort at least.

in your reply there would definitely have to be the hose setup i think. its just to hot under to not take advantage of the cold air intake system.


thanks for the reply i really appreciate it.

 

go to RX7.com and under the intake category, thers a product called the RP fresh air headlight cover.

its a panel that replaces the cover on ur pass side headlight, made out of fiberglass, and has a scoop built into it, and w/ ur cone filter in the place of ur original filter box, this scoop will let cold fresh air into the engine compartment, and get sucked right up by ur new cone filter. its lik e$56 usd. its worth it. besides, less work, less fabrication, and less weight than makin ur own intake ducting.

chris

 

thanks for the reply.

i wasnt thinking anything fancy as far as fabricating anything. just a kind of patch and go wedge of some sort that diverts air up towards the intake chamber as im driving. because its got a seal covering the intake area when the hood is down i think it would be reasonably efficient(i hope).

also i believe it wouldnt cost more than 10 bucks to fit something in. although id like to have that fiber headlight and cone filter i cant really justify the expense to myself when the intake system i have is quite good i think(as long as i can get some damn air flow in there .

yoiur idea will certainly be one to consider should this prove more difficult than i anticipate, or it just doesnt improve the result. thanks again for the response.

 

fyi; as soon as i switched from my original set up to this cone filter, it made a NOTICABLE difference. i could definitly tell. right now, itsjust a straight shot thru the AFM. w/ the original set up; its got curves and bends, and has to make 2 90* bends. one as it enters the air filter box, and the other as it turns to go thru the AFM...not good for intake velocity. and the little chambers that are on ur intake pipe under the front of ur hood. those are expansion chambers, and are only there to quiet down the intake noise, not for performance.

then again, ive got a K&N filter from a toyota MR2 turbo, so its 2x as big as anyone elses filter. its got like an 8" base, and 8" tall...its Huge.

so if u want, order a filter and adaptor for a Mk2 toyota Mr2 turbo. they use almost the exact same AFM, so itll bolt right up to our cars.

anywho, good luck

chris

 

thanks for the advice. i see your point about the 2 x 90 degree turns... that cant be all to efficient

question: is there any problem shooting that much air into the chamber? maybe sending more than is neccessary for a proper air/fuel mixture? or does the filter only let in what is needed?

just looking to avoid any possible problems before they pop up....

thanks again.

 

or does the air flow meter dictate how much air gets in? im not to sure exactly what the air flow meter does(aside from obviously monitoring air flow...).

thanks

 

the engine only sucks as much air as it needs.

but if u combine a low restriction intake, and low restriction exhaust together. like, a gutted cat/racepipe and a straight thru muffler. then chances are, youre engine will be able to ingest more air than it did originally. see the computer is programmed to operate w/ the restrictive intake and exhaust, so its only gonna be delivering fuel for the amount of air that it is programmed for.

so, its MY belief, that as soon as u can suck in more air, that you should tell the computer to inject a little more fuel to prevent it from leaning out. see, the rx7 already runs a little on the lean side in the middle RPMs. and letting the engine move more air into itself w/o adding the additional fuel, might make it run lean. which means ur not makin as much power as u could be.

the air flow meter, measures how much air the engine is sucking in. the more air going in, the more fuel it will tell the engine to add. there is a way to adjust, or offset, the meter so that the engine thinks its flowing a tad more air than it really is. this will make the computer at a little more fuel than it normally would. and, this would make it run a little more Richer, and probably get rid of the lean problem. theres alot of guys here that think you should not mess with, tinker with, or even fiddle w/ ur AFM. cuz if somethign goes wrong, its really expensive to replace. so, you probably shouldnt mess w/ it. hope that answers ur questions.

chris

 

yup that answers it perfectly. thanks.

btw, would larger fuel injectors take care getting extra fuel in there(besides modifying the settings on the AFM)? or does the AFM regulate how much fuel the injectors push as well?

 

If you have an N/A you really do not need to worry about getting more fuel in there. Upgrading the intake and exhaust to flow more will cause more air to enter the engine, but that's why the MAF (mass air flow) sensor (AFM is actually air/fuel meter I think) is there. It tells the ECU that more air is going through, and the ECU automatically adds more fuel. I am told the N/A ECU can handle up to about 5 PSI of boost, but this is a more controversial subject. I was thinking of finding a supercharger at a junk yard and fabricating a way to hook it up to run about 4 PSI, and I might still do that, but I have been talking to a bunch of people about it. Some think it's a good idea, some think it's bad. We'll see. I'm not doing any kind of boost without an air/fuel meter, and I have Jef Card helping out with all of the planning.

Basically, you don't need to worry about fuel with an N/A because the ECU will take care of it.

 

my whole interest in bigger injectors is really to find out if that is all you need done as far as the injection system to handle turbo/supercharing. would i need a fuel pump able to pump more fuel at all as well if thats the case?

 

HUggybear, heres the low down on the stock fuel system.

its capable of supporting 200HP at the flywheel, quite safely and reliably.

if u do mods to increase ur power over 200HP, youll need to jump up to bigger injectors, and a fuel pump w/ increased output.

the reason for this IS, if u are trying to support massive amounts of HP w/ ur stock fuel system, it will try to keep up, cuz the ECU can accomodate. but the injectors simply wont be able to push as much fuel, the max efficiency rating w/ max reliablility is 87% duty cycle. if u try to support MORE hp than u can w/ the stock injectors, the ECU will increase the duty cycle of the injectors Past 87%. this will cause the injectors to run erratically, and possibly hang open, causing damage to the injectors, and its generally just BAD.

but, if u upgrade ur fuel injectors, youll need the bigger fuel pump. cuz, what good are huge injectors gonna do ya, if u cant FEED them?! see what i mean?

the Stock AFM should be good for anything you have planned as far as mods go, unless you get radical, w/ port matching, and street porting, which probably is a WAYS off from ur plans.

Chic: just curious, what happens when u reach the point where the AFM doesnt measure any additional air? say ur flowing SOOO much air, that the AFM door is Wide Open, and any additional air that flows past it, is not being quantified. and the computer doesnt know its THERE, and therefore, wont add the proper amount of fuel. you think this is ever a problem?

chris

 

The door on the MAF is either open or closed. When it's open, it has a method of seeing how much air goes by. There is also a pressure (boost) sensor even on N/A cars that will see any type of pressure or change in the density of the air. With those two inputs to the ECU, it can see all of the air going into the engine.

 

are the increased capacity injeactors and fuel pump what i would be looking for to support turbo/supercharging this car? is that whats meant by "aftermarket fuel injection"? or is there something else i need too?

also, if my car was over 200 HP by chance what would be some of the symptoms of problems that could be experienced?

iv got this issue where when i pull off the line it goes all right for a fraction of a second, hesitates and then pulls forward again. feels like it just loses power, and then picks up again. with the duel exhaust and no cat converters i have im not sure how much my actual HP is and if this hesitation may be due to more HP than what can be handled. id be shocked if this car was over 200HP but im desperate to find out whats causing this.

i thought it might be the air filter but i dropped in a K&N and same problem. now i think maybe deposits in the throttle body or something holding things up(btw whats the best method/material to use to clean out the TB?). this has been plauging me from day 1 with the car.

BTW, id lik to street port this thing, but i cant justify the gains vs cost of pulling the the engine apart just for that. as soon, if ever i need to have work done on it, like a rebuild or something, ill port it then. whats wrong with the AFM if its street ported?

thanks

 

it sounds like ur bogging off the line. try revving ur engine to 4k RPM, and then dumpin the clutch. youll have a little tire spin, and as soon as that diminishes, floor it. i think what happend is, that w/ ur low restriction intake, and exhaust, your car's powerband has moved further up the RPM range. which means, you need to rev ur engine a little higher than before, in order to get ur added horsepower. its a fact of life, these cars when modded, dont really have any ***** below 3000 RPM. above that is where it gets beefy.

aftermarket fuel pump means, buy a high output, high volume fuel pump made by a company that is NOT mazda. Walbro fuel pumps seem to be really popular.

all you can really do to clean off ur TB, is remove it, and clean it by hand. you can take it off, and let it soak in a bowl full of carb cleaner. that will get rid of most of the gunk.

CHIC: so, we can turbo our car w/ the stock intake? is this 'boost sensor' by anychance, the little black box mounted on the pass side strut tower w/ a sticker saying 'boost sensor' on it?cuz i think i have one of those...

so its only good up to 5psi eh? soo....is there a diff 'boost sensor' i can swap in place,that would be effective up to a max of 10 psi? just curious.

chris

 

flubyux:

unfortunately i cant get this to go away at all. even reving up to 6-7k RPM i still get that power loss after dropping the clutch. its not quite so noticeable at these times though.

it prevents that sweet start off the line id like so much

 

Speaking from experience, the stock ECU, MAF, and boost sensor on an NA will be able to handle moderate levels of boost. At top end, I'm pushing 10psi on all stock electrical. Fuel I've had to modify, I've got the Rotary Performance upgraded fuel pump, and I've swapped the stock 460cc/min for 550cc/min from a TII. The computer is just fooled and I actually run rich. Each of the three times I've dyno'd with this setup, I've gotten 210hp, 200hp, and 205hp at the rear wheels. With the same supercharger setup but without the bigger injectors/pump, I only dyno'd ~175hp at the wheels and started to run lean and get detonation.

Oh yeah, rather than dumping the clutch, try feathering it while keeping your rpm's above 4000. Prior to adding the blower I found that worked pretty well.

 

ya i can tease the clutch a bit to avoid it if i try. something about going back, and forth, and back again on the clutch makes me think theres a problem.

with this ground fix for the 3800rpm work for this? if anyone knows?

 

the classic 3800 RPM stutter/hesitation is typically fixed by grounding the chassis of the ecu to the car body, and also grounding the battery directly to the frame of the car, and then the frame, to the engine block.

however, my friend has an 87 T2, w/ a stutter around 3800, and hes already done the grouding tricks, yet it still has the problem. what could that be caused by??

sweet, i can boost my motor w/ the stock electronics! just need to find bigger injectors and pump eh?

chris