Open element, or Cold air intake?

[sandawgk5]

With all of this cold air talk I thought the TBI was designed to run with some temp and colder air actually made the not work quite right. That is why they have 195F thermostats in most TBI engines.

To the OP I just turn my lid upside down and run a ghetto open element until I take it to the smog station then I just flip the lid over

Dik

 

[dyeager535]

TBI doesn't measure inlet air temp, it only measures engine temp. If the ENGINE temp is too low, the ECM esentially "chokes" the engine by adding more fuel than required, making it run richer than is actually necessary. I haven't looked at the PROM of a TBI engine in awhile, only thing I remember is that somewhere around 120* engine temp in some applications is where it looked like GM decided "choke" was no longer necessary by the way the PROM was setup.

Higher engine temps actually make more power, but you've got a bit of a catch 22 here...hotter incoming air keeps fuel atomized, theoretically leading to better efficiency in burn, while colder air is denser, theoretically leading to more power. So hot intake walls are a plus, but so is colder air. As much as any of us like to spout theory, the reality is without EXTENSIVE dyno testing of each possibility, which isn't really possible anyways, there is no way to know for certain. That's not even getting into the density vs. volume discussion keeping this post alive.

The G-tech mentioned is about as scientific as anyone has gotten so far it looks like. I tried flipped lid, single snorkel, dual snorkel, none of them did anything mileage-wise, which I check every tank. Different noise levels yes, more efficiency no.

 

[ryoken]

like Ryoken's planning.

It's funny how things come about... This all started with me cleaning and organizing the attic..

I had already decided to go with the all glass clip, for a few reasons.. Upon digging out the door, cage and vac actuator assembly (just need the hinges and other tidbits) from one of my old Chevelles, I got the idea...

I already knew I was going cowl induction glass, so it was an obvious evolution.. It's a perfect mod for me and my composite sheet glass... similar techniques to my shroud, box, etc...

I always loved the novelty of the flapper on my Chevelles and thought it'd be something trick and different on a truck... I'm doubting it's been done, at least I haven't seen it...

It will only be vac operated tho, no full throttle switch... I'll have the vac solenoid tied in with the vac gauge I'm gonna run under the back lip.

I still have some items ahead of this on the purchase list.. headers, shocks, etc.. But I plan to order the front clip in the next couple months... I actually don't expect this to be THAT difficult a mod.....

 

[noJeepshere]

one benefit of a CAI is the cooler outside air is denser, and has more oxygen per cubic inch. thats the whole thinking around them. my 81 sucks to drive on a hot day becuase of the open element that i have. nerdy me, i actually conducted a test of this theory, i have a remote sensor thermometer that i put in the air intake on my dads 98 sub. with the cover off, the underhood temp in 93*f outside was ~140-160* in town and ~110* on the road (the sensor maxed at 160*, so it could be higher.) with the cover on, it was around ~110-125* around town and ~100 on the road. getting cool air (that is denser and more oxygen rich) is really beneficial to your ride. a snorkel would be even better because it has a dual ram air and cool air effect. the higher off the ground you can pick up your air, the cooler itll be.

 

[noJeepshere]

I may draw the line at the smaller filters. GM decided in the early 80's that they'd go with the "tall" filter on some of the trucks, and many of those seemed to be 305's. (my '83 for instance)

i wonder if gm did that thinking the smaller displacement trucks would be more working vehicles and a larger filter took longer to fill up with dirt.

 

[dyeager535]

I think it was more likely due to GM's attempt to phase out the 350's, anything to make the smaller motors feel bigger.

GM was pretty consistent in the 80's on the smaller V8's in putting 800CFM carbs in them, which by most would be too much, but it apparently helps torque production. I'm not sure how long GM ran the two filter sizes concurrently on the same CID, if they did at all.

 

[Hogback Fabrication]

GM was pretty consistent in the 80's on the smaller V8's in putting 800CFM carbs in them, which by most would be too much, but it apparently helps torque production.

A bigger carb should always make more power on any motor (as long as its fuel requirements are in the tunable range).

When you hear people talk about a carb being too big for a motor its because big carburetors make drivability and part throttle pretty poor on a motor that doesn't "need" it.

 

[Blue85]

It will only be vac operated tho, no full throttle switch... I'll have the vac solenoid tied in with the vac gauge I'm gonna run under the back lip.

Obviously a straight vacuum connection will open your flapper only at idle / low throttle. So you will store vacuum somewhere and use a solenoid to open the flapper when engine vacuum drops or will it be open anytime the engine is running? It shouldn't be any harder than keeping the HVAC vacuum motors working under heavy throttle, which already works.

 

[ryoken]

they are set up just the opposite... at idle with vacuum, it's closed.. under throttle or when the motor is off, it's open..

creating vac pulls the door closed.. I know it's a little goofy, but thats how they're setup.. it's cool when you goose the throttle and it opens and closes..

take a peak at a Chevelle sometime when its parked, the flapper will be up...

 

[jonrpick]

I think it was more likely due to GM's attempt to phase out the 350's, anything to make the smaller motors feel bigger.

GM was pretty consistent in the 80's on the smaller V8's in putting 800CFM carbs in them, which by most would be too much, but it apparently helps torque production. I'm not sure how long GM ran the two filter sizes concurrently on the same CID, if they did at all.

Yeah... but those were Q-Jets... I haven't conducted back-to-back tests, but I'm betting that switching from a Q-Jet to a 800cfm square-bore carb would make a noticeable difference in low-end torque production and fuel economy. As least, logically that's the conclusion I come to since the smaller primaries are better at lower engine speed in producing high speed air movement.

 

[dyeager535]

Primary side on the Q-jet is whats different between the 750's and 800's. But you are right, a "square bore" carb would be 100CFM larger on the primary side, if they even have such a thing. 800 Q-jet is 300 on the primary, 500 on secondary.

As mentioned, easier to tune, which means better driveability. Still, if engine demand is enough, theoretically all 800CFM could be used, it really has no bearing on engine size. I don't know what David Vizard was testing, but that's what he found out, even going with a carb that by calculation was too big, the tested engine continued to make power. IIRC the carb was 1000CFM by the time he stopped going up in size, the engine was perhaps a small block.

In any case, check out what a bone stock 305 is SUPPOSED to like CFM-wise based on the numerous calculators out there, and compare that to the size of carb GM was putting on 305's and 307's (Olds). You see 500CFM being thrown around as the "optimal" size for a 350 carb quite regularly, obviously that isn't correct, or GM would have done it. Of course, with better fuel management (injection) the smaller engines were choked down to the 500CFM range.