Custom built Venturi intake, using garbage scraps

Return your intake to stock until you figure out this problem.

It sounds to me like you have a dirty or dying MAF sensor, and/or a vacuum leak. Check all of the vacuum hoses and rubber ends for cracks.

I really REALLY think you should not add a venturi in the ductwork before your MAF sensor. That sensor is critical to engine function and messing with airflow before the sensor can have very undesired results.

deekster_caddy wrote:

Return your intake to stock until you figure out this problem.

It sounds to me like you have a dirty or dying MAF sensor, and/or a vacuum leak. Check all of the vacuum hoses and rubber ends for cracks.

I really REALLY think you should not add a venturi in the ductwork before your MAF sensor. That sensor is critical to engine function and messing with airflow before the sensor can have very undesired results.

problem is I don't even know where the stock intake parts are anymore. would my intake setup before I had the venturi work as well?

Also, how does the L67 cope with boost from a supercharger if any type of boost is going to mess with the MAF?

so the only way to diagnose the MAF is unplug it and see if anything changes?

c0reyl wrote:

Also, how does the L67 cope with boost from a supercharger if any type of boost is going to mess with the MAF?

so the only way to diagnose the MAF is unplug it and see if anything changes?

I'm not sure that I'd rate your venturi as "boost", but the difference between the two is for the L67, the air is drawn through the MAF evenly. For the sensor to read correctly there needs to be laminar airflow. Your ventiri while increasing velocity, will put that increase at a hotspot starting at the middle of the 3.5" and then washing to the side where the pipe bends just before the TB. This throws off the sensors reading VS. actual air flowing through. For version 2 of it I would suggest having the inner tube matching the 3.5" TB DIA to negate this. Then the velocity is increased across the entire pipe cross-section. I'd also like to point out that the venturi effect in your design is really only useful at WOT, since at part throttle the TB plate causes more disruption than the venturi effect overcome.


And yes, the best way to diagnose the MAF is unplug it. The difference should be very noticeable. The only other way is using a scan tool to read the value of the sensor at various throttle positions. Unplugging it is sort of an instant check.

Karma wrote:

c0reyl wrote:

Also, how does the L67 cope with boost from a supercharger if any type of boost is going to mess with the MAF?

so the only way to diagnose the MAF is unplug it and see if anything changes?

I'm not sure that I'd rate your venturi as "boost", but the difference between the two is for the L67, the air is drawn through the MAF evenly. For the sensor to read correctly there needs to be laminar airflow. Your ventiri while increasing velocity, will put that increase at a hotspot starting at the middle of the 3.5" and then washing to the side where the pipe bends just before the TB. This throws off the sensors reading VS. actual air flowing through. For version 2 of it I would suggest having the inner tube matching the 3.5" TB DIA to negate this. Then the velocity is increased across the entire pipe cross-section. I'd also like to point out that the venturi effect in your design is really only useful at WOT, since at part throttle the TB plate causes more disruption than the venturi effect overcome.


And yes, the best way to diagnose the MAF is unplug it. The difference should be very noticeable. The only other way is using a scan tool to read the value of the sensor at various throttle positions. Unplugging it is sort of an instant check.

oh, I know it's nowhere near like real boost, but I have noticed a difference in higher RPM. I'll ask my step dad to help me diagnose the MAF in a while. He has a scan tool

what I don't get is I never see anyone with a weapon R intake having this happen, so either A: the venturi in a weapon R is bullshit, or B: somehow my venturi actually works, which I don't get because I made it out of garbage scraps :3

Actually my guess, and you might not like it, is your venturi is actually acting as an intake restriction. It works better with it in because your MAF is going out and responds to less airflow better. Hense why it ran better when your step dad covered part of the filter.(Which should never happen, no such thing as too much airflow at idle when the engine is breathing on its own properly.) More airflow makes it hit the range where it has a dead spot or incorrect readings making the engine feel down on power. The change in intake is just obscuring an existing problem, so you have no baseline to decide on its pros/cons.

For checking out the MAF, even if the values seem ok with the scan tool at various throttle ranges, unplug the MAF anyway and go for a drive. Its a fast easy way to check, and will answer a few other questions for people trying to troubleshoot your problem. Then once you have done the unplug MAF test, you can clear the code that it will set again with the scan tool.

alright, I'll unplug the MAF and see if my performance changes

For some ideas look at what the Japanese and European litre bike builders are doing now to get nearly 200 RWHP out of 1000cc's with no boost. It's all about making the intake charge flow fast enough to pressurize the inlet tract, creating a pseudo supercharger. Much of this cannot be practically done on our engines since it's an integrated system from air filter to valve seat but I firmly believe in stealing from the best.

c0reyl wrote:

deekster_caddy wrote:

Return your intake to stock until you figure out this problem.

It sounds to me like you have a dirty or dying MAF sensor, and/or a vacuum leak. Check all of the vacuum hoses and rubber ends for cracks.

I really REALLY think you should not add a venturi in the ductwork before your MAF sensor. That sensor is critical to engine function and messing with airflow before the sensor can have very undesired results.

problem is I don't even know where the stock intake parts are anymore. would my intake setup before I had the venturi work as well?

Also, how does the L67 cope with boost from a supercharger if any type of boost is going to mess with the MAF?

so the only way to diagnose the MAF is unplug it and see if anything changes?

The L67 has the MAF sensor before the supercharger, so it is measuring outside air being drawn in through the intake, not compressed air.

A MAF sensor will work with just about any smooth pipe feeding it. But you have added a massive amount of turbulence right before the MAF sensor, which requires smooth air passage to work properly. That's why on the OEM throttle body there is a screen with a bunch of honeycomb shaped holes in it, to straighten out the airflow before it hits the MAF sensor. (some people think that screen is a restriction too, but the designers at GM think smooth airflow is more important... there is plenty of airflow through that screen for most applications)

Also, take a close look inside your throttle body if you have a chance - notice how the throttle plate opening is much smaller than the intake duct opening you are messing with. The reduced opening size causes a venturi effect happening right there, AFTER the MAF sensor, combined with the throttle plate.

I never got around to taking out the MAF sensor yet, been kinda busy lately, but when I went to go grab my mom something from a gas station, I decided to punch it to see if being colder out affected anything, and it really did, so I think my main problem is the intake getting hot air affects the venturi setup more than anything else, it was pretty hot out when I first tested it, I'll still see what's up with the MAF though :3

Btw, air temp sensor goes as close as possible to the filter, right?

air temp sensor location isn't super important, as long as it's after the air filter. Closer to the MAF is okay. Newer MAF sensors (different vehicles) have the air temp sensor and MAF sensor combined in one unit. (google for images of "LQ4 MAF sensor" to see what I mean)

If you were to swap MAF sensors to that unit, you would also need to change the MAF tables in the PCM, requiring some programming.

BTW Please create and activate your signature so we can see easily/quickly what year your car is and other important specs. The 95 cannot have it's tables reprogrammed for a different MAF sensor as far as I know.

deekster_caddy wrote:

air temp sensor location isn't super important, as long as it's after the air filter. Closer to the MAF is okay. Newer MAF sensors (different vehicles) have the air temp sensor and MAF sensor combined in one unit. (google for images of "LQ4 MAF sensor" to see what I mean)

If you were to swap MAF sensors to that unit, you would also need to change the MAF tables in the PCM, requiring some programming.

BTW Please create and activate your signature so we can see easily/quickly what year your car is and other important specs. The 95 cannot have it's tables reprogrammed for a different MAF sensor as far as I know.

I now have a fenderwell cold air venturi setup. I'll see if this helps, if it doesn't, I'll delete the venturi for a while and figure out the root problem

grisolm1 wrote:

For some ideas look at what the Japanese and European litre bike builders are doing now to get nearly 200 RWHP out of 1000cc's with no boost. It's all about making the intake charge flow fast enough to pressurize the inlet tract, creating a pseudo supercharger. Much of this cannot be practically done on our engines since it's an integrated system from air filter to valve seat but I firmly believe in stealing from the best.

Thanks, I'll definitely look into it



UPDATE




Now a cold air fenderwell venturi setup. I'll see if the colder air helps.

grisolm1 wrote:

For some ideas look at what the Japanese and European litre bike builders are doing now to get nearly 200 RWHP out of 1000cc's with no boost. It's all about making the intake charge flow fast enough to pressurize the inlet tract, creating a pseudo supercharger. Much of this cannot be practically done on our engines since it's an integrated system from air filter to valve seat but I firmly believe in stealing from the best.

Yes, but where are those bikes making that 200 HP? The faster you can turn an engine, the more HP it will make as long as it can breathe at higher RPM. Look at motorcycle red lines, anywhere from 10,000 -19,000 RPM.

I'm not really sure a venturi will work on the atmospheric side of the intake. To me, it's more of a restriction than anything else. The way to make power is to increase port velocity inside the engine. That is what head porting is all about. An engine is an air pump. The more air you can get in and out of it, the more power it makes.

hey coryel,why dont you have your eprom chip re-calibrated? Go to sinisterperformance.com. they will fix you right up.

[quote="LARRY70GS"]

grisolm1 wrote:

Yes, but where are those bikes making that 200 HP? The faster you can turn an engine, the more HP it will make as long as it can breathe at higher RPM. Look at motorcycle red lines, anywhere from 10,000 -19,000 RPM.

I'm not really sure a venturi will work on the atmospheric side of the intake. To me, it's more of a restriction than anything else. The way to make power is to increase port velocity inside the engine. That is what head porting is all about. An engine is an air pump. The more air you can get in and out of it, the more power it makes.

Horsepower is nothing more than a measurement of power over time, the formular of which, is Torque times RPM, divided by 5250, then gearing multiplies torque to allow the powerplant to more effectively put the power down. this is why a Honda with barely any more torque than those bikes can go fast


by the way, I never claimed to get huge amounts of power from the venturi, I will claim however that my throttle response is greatly improved, and even more so with the cold air intake setup I just in combined with it. I plan on cleaning my throttle body more and picking up a 180* tstat some time soon.

robotennis61 wrote:

hey coryel,why dont you have your eprom chip re-calibrated? Go to sinisterperformance.com. they will fix you right up.

What exactly does that do, reprogram my ECU? if so, I'm interested in changing the shifting to be more aggressive instead of as sluggish as it is. I hate when I step on it and it's stuck in 3rd

Also, how much does it cost? I can't really find much info about it

Exactly, RPM X TQ divided by 5252 = HP. More RPM makes more HP. No argument there. Honda engines are operated at higher RPM to make that HP.


What I am saying to you, is that your venturi on the intake side may speed up the air entering the engine, and you may feel an increase in throttle response, but ultimately, it will be a restriction on the intake side, and will sacrifice higher RPM HP. I think if you ran that car down the 1/4 mile with and without your device, you would see a big difference in trap speed and E.T.

That's where I put my filter for my FWI, you'll definitely hear it! I keep forgetting your engine isn't supercharged, otherwise I was going to suggest getting a slightly longer filter.

To those arguing: I don't think he meant for the Venturi intake to double his horsepower, it's just neat that he built one himself and is using it. It doesn't severely restrict airflow to the engine, and of course the best way to modify the intake is to port the heads, but that requires taking the engine apart and access to a professional machine shop.

LARRY70GS wrote:

Exactly, RPM X TQ divided by 5252 = HP. More RPM makes more HP. No argument there. Honda engines are operated at higher RPM to make that.


What I am saying to you, is that your venturi on the intake side may speed up the air entering the engine, and you may feel an increase in throttle response, but ultimately, it will be a restriction on the intake side, and will sacrifice higher RPM HP. I think if you ran that car down the 1/4 mile with and without your device, you would see a big difference in trap speed and E.T.

I'm okay even if I do lose a little top end, which I think I'm not. keep in mind, my riv has an L36, and this is not actually a restriction to my intake system. I didn't just put a funnel in the intake and call it a day, there's a copper pipe to let the air pressure difference even out, to allow velocity to increase properly.




You can see that here.

IBx1 wrote:

That's where I put my filter for my FWI, you'll definitely hear it! I keep forgetting your engine isn't supercharged, otherwise I was going to suggest getting a slightly longer filter.

To those arguing: I don't think he meant for the Venturi intake to double his horsepower, it's just neat that he built one himself and is using it. It doesn't severely restrict airflow to the engine, and of course the best way to modify the intake is to port the heads, but that requires taking the engine apart and access to a professional machine shop.

I definitely do hear it, and I'm glad you get the point I got this filter for free by the way, and my friend even cleaned it out before, and was just too impatient to wait for dry time lol. I figured I'd use it until I get a supercharger

since I just made the fenderwell intake setup, torque works way better, and properly now, and top end is improved from stock as well. I just need a better tstat and need to find a good tool to make a perfect hole in the plastic sidewall for the temp sensor :3

IBx1 wrote:

To those arguing: I don't think he meant for the Venturi intake to double his horsepower, it's just neat that he built one himself and is using it. It doesn't severely restrict airflow to the engine, and of course the best way to modify the intake is to port the heads, but that requires taking the engine apart and access to a professional machine shop.

I'm not trying to argue with Corey, and I think it's interesting to try new things. That is how we learn. I do however think that it will restrict air flow at higher RPM despite the fact that it might offer improvements off idle and at low RPM. I think you would see that in track testing.

Venturis are what make a carburetor work. By speeding up the air, you get a pressure drop inside the carburetor. The fuel in the bowl is acted on by atmospheric pressure, and that is what causes fuel flow. Take a look at a Quadrajet 4bbl carburetor. The primary side of the carburetor has a triple venturi cluster to promote a very strong signal, and it takes very little throttle movement to initiate fuel flow, but the secondary side of the carburetor is huge, with no venturi for maximum power at high RPM wide open throttle. The venturi entry and exit angles are very critical in regaining some of the pressure lost from the venturi design. The carburetor manufacturers did a lot of R&D developing those entry and exit angles.

Like I said, Corey might feel a throttle response improvement, but ultimately the engine would be breathing through a restriction when it needed the most air.

LARRY70GS wrote:

IBx1 wrote:

To those arguing: I don't think he meant for the Venturi intake to double his horsepower, it's just neat that he built one himself and is using it. It doesn't severely restrict airflow to the engine, and of course the best way to modify the intake is to port the heads, but that requires taking the engine apart and access to a professional machine shop.

I'm not trying to argue with Corey, and I think it's interesting to try new things. That is how we learn. I do however think that it will restrict air flow at higher RPM despite the fact that it might offer improvements off idle and at low RPM. I think you would see that in track testing.

Venturis are what make a carburetor work. By speeding up the air, you get a pressure drop inside the carburetor. The fuel in the bowl is acted on by atmospheric pressure, and that is what causes fuel flow. Take a look at a Quadrajet 4bbl carburetor. The primary side of the carburetor has a triple venturi cluster to promote a very strong signal, and it takes very little throttle movement to initiate fuel flow, but the secondary side of the carburetor is huge, with no venturi for maximum power at high RPM wide open throttle. The venturi entry and exit angles are very critical in regaining some of the pressure lost from the venturi design. The carburetor manufacturers did a lot of R&D developing those entry and exit angles.

Like I said, Corey might feel a throttle response improvement, but ultimately the engine would be breathing through a restriction when it needed the most air.

first of all, my engine doesn't need near the amount of airflow as a supercharged buick does, huge important note, and the pipe to allow pressure difference has a much larger inner diameter than a weapon R by the way

secondly, I got some torque I really needed for the long gears to accelerate. the car now is faster than it ever has been, and I had an intake setup without venturi before.

c0reyl wrote:

LARRY70GS wrote:

IBx1 wrote:

To those arguing: I don't think he meant for the Venturi intake to double his horsepower, it's just neat that he built one himself and is using it. It doesn't severely restrict airflow to the engine, and of course the best way to modify the intake is to port the heads, but that requires taking the engine apart and access to a professional machine shop.

I'm not trying to argue with Corey, and I think it's interesting to try new things. That is how we learn. I do however think that it will restrict air flow at higher RPM despite the fact that it might offer improvements off idle and at low RPM. I think you would see that in track testing.

Venturis are what make a carburetor work. By speeding up the air, you get a pressure drop inside the carburetor. The fuel in the bowl is acted on by atmospheric pressure, and that is what causes fuel flow. Take a look at a Quadrajet 4bbl carburetor. The primary side of the carburetor has a triple venturi cluster to promote a very strong signal, and it takes very little throttle movement to initiate fuel flow, but the secondary side of the carburetor is huge, with no venturi for maximum power at high RPM wide open throttle. The venturi entry and exit angles are very critical in regaining some of the pressure lost from the venturi design. The carburetor manufacturers did a lot of R&D developing those entry and exit angles.

Like I said, Corey might feel a throttle response improvement, but ultimately the engine would be breathing through a restriction when it needed the most air.

first of all, my engine doesn't need near the amount of airflow as a supercharged buick does, huge important note, and the pipe to allow pressure difference has a much larger inner diameter than a weapon R by the way

secondly, I got some torque I really needed for the long gears to accelerate. the car now is faster than it ever has been, and I had an intake setup without venturi before.

OK, I wish you luck.

LARRY70GS wrote:

c0reyl wrote:

LARRY70GS wrote:

IBx1 wrote:

To those arguing: I don't think he meant for the Venturi intake to double his horsepower, it's just neat that he built one himself and is using it. It doesn't severely restrict airflow to the engine, and of course the best way to modify the intake is to port the heads, but that requires taking the engine apart and access to a professional machine shop.

I'm not trying to argue with Corey, and I think it's interesting to try new things. That is how we learn. I do however think that it will restrict air flow at higher RPM despite the fact that it might offer improvements off idle and at low RPM. I think you would see that in track testing.

Venturis are what make a carburetor work. By speeding up the air, you get a pressure drop inside the carburetor. The fuel in the bowl is acted on by atmospheric pressure, and that is what causes fuel flow. Take a look at a Quadrajet 4bbl carburetor. The primary side of the carburetor has a triple venturi cluster to promote a very strong signal, and it takes very little throttle movement to initiate fuel flow, but the secondary side of the carburetor is huge, with no venturi for maximum power at high RPM wide open throttle. The venturi entry and exit angles are very critical in regaining some of the pressure lost from the venturi design. The carburetor manufacturers did a lot of R&D developing those entry and exit angles.

Like I said, Corey might feel a throttle response improvement, but ultimately the engine would be breathing through a restriction when it needed the most air.

first of all, my engine doesn't need near the amount of airflow as a supercharged buick does, huge important note, and the pipe to allow pressure difference has a much larger inner diameter than a weapon R by the way

secondly, I got some torque I really needed for the long gears to accelerate. the car now is faster than it ever has been, and I had an intake setup without venturi before.

OK, I wish you luck.

Lol, this intake setup is just me messing around until I get a supercharger put in, also, having a 9.4:1 compression ratio makes me gain a bit more power from an intake mod than a supercharged buick with an 8.5:1 ratio I believe

Update: this seems to have fixed my problem entirely.

Good discussion, from two different sides of mod logic. One school says that numbers rule. If you can't verify quantitatively that changing the system results in an actual gain in power or track times, the numbers people say it isn't worth doing. The other group says experimentation and DIY mods can instill a sense of pride and personal accomplishment, regardless of the actual results. If it feels right to the owner, why do numbers even matter?

Both sides offer real benefits to different types of folks. As Einstein would profess, it's completely relative. For those guys who've been to the track, and have seen first-hand what makes a car faster, it's a no-brainer what mods you do and don't do to a car. For the other guys looking from a different angle, why not try things for the experience, even if the numbers guys snicker? As most everyone knows, true innovation often results from experimentation against traditional logic. Who knows? Trying something opposite the norm could result in spectacular discovery!

One problem with the numbers type of approach is that verification requires a visit to the track, or metering with expensive equipment such as a dyno. This often costs as much or more than the mods themselves, and not everyone has the time or means for it, so most people looking for proven gains will pay their money to a professional with a good reputation for a claimed result. Most of the time you get what you pay for, but how do you really know? Because you're detached from the mod process, you're putting 100% trust in the one doing the work. My advice: unless you know from reputation or experience that your guy knows his stuff, ask for some kind of proof to verify the numbers are legit.

In contrast, the DIY experimenter types are basically using trial & error methods to offset the cost of professional equipment or services. Using what fundamental knowledge they have (or think they have), these folks prefer to try new things, tinker with settings, and experience results, which are usually felt rather than recorded. The obvious problem here is that time can be wasted, with no guarantee on return. In many cases, you can end up with a car that's less reliable, slower even, than what came from the factory. As Larry70GS has pointed out, the engineers at GM knew a thing or two about this sort of stuff. If we assume they are wrong about everything, we are probably fooling ourselves.

My opinion is this: you need to pull from both sides. Feel free to experiment, but be smart - understand that numbers do matter, and that your perception of "improved response" is kind of like saying your favorite color is blue. Try to find a more objective way to verify results without spending much money, then your findings will become more credible. Member opinions on our board can vary somewhat, but some things we all agree on, and this is FREE info! Consider the opinions of those like Larry70GS, who have years of experience tuning cars and running at the track. Don't agree with what he has to say? Try proving him wrong then. Take some base-line measurements and then try implementing your mods under same situations, and compare results. Be careful to do your testing in a scientific manner, and repeat more than once to show consistency. Because you're involved in the testing, whatever results you find, at least you'll learn something. If the results are not what you wanted, NO BIG DEAL. The most intelligent thinkers in history will say they learned the most from occasional failures.

Regarding your progress so far, it is intriguing work. I know very little about the behavior of air intakes on NA engines, and would like to know more. Admittedly, I'm a numbers guy, but I do appreciate experimentation. Would like to see some numbers that prove your intake design really functions in practice as it does in theory. I want to know if that copper pipe actually does what you think it does (letting the air pressure stabilize). Right now, we have no evidence it works in your particular case. No saying it doesn't, because I have no proof that it doesn't. Right now, it's just a copper pipe that might do as intended.

Last thought: you mentioned your intent to drop the t-stat to a 180º unit. Based on my own experience, and what I believe to be excepted wisdom from those that know, you won't see any performance benefit from doing this, unless you can find a way to advance spark timing to a point where engine starts to knock. All engines are designed to operate most efficiently within a certain temperature range; in our case, that's about 190-210ºF. For supercharged applications, we are constantly flirting with knock under boost, and since forced induction is a definite power adder, it makes sense to compromise thermal operating efficiency a little but in order to improve the blower's ability to add power, ei. fighting spark knock to allow more boost. But if you're not fighting knock, it's not helping, and probably hurting performance.

Keep us updated on your progress. Feel free to start new threads or add to old ones when you experiment with different areas of the engine or car.

There is a very simple test that anyone can run with a vacuum gauge on a normally aspirated engine. Vacuum gauges are easily affordable to anyone, and are an excellent diagnostic tool that should be in the tool box of anyone who works on engines.

Pretty simple. Hook the gauge to a source of manifold vacuum. Tape the gauge to the windshield so that you can see it while driving. Do some wide open throttle runs, and note the vacuum reading at WOT. If there is a restriction on the intake side, there will be more vacuum at WOT than with no restriction. Ideally, vacuum should be 0 or very close to it. A reading of more than 1 or 2" of vacuum indicates a restriction. On the older cars, it is an indication that the carburetor is too small, and is offering a restriction to flow.