New project

[Chevy1925]

Glad to hear she's still running!

It looks like my MAP sensor can only handle about 15psia before it's maxed out so more than likely it wont like it. The sensor is mounted in the intake manifold but I can remote mount it. How exactly are you clamping it off? Something like a PPE boost fooler with a one-way check valve? So any time there is pressure the check valve just relieves it? I just did some lunch time logging on it with a Tech II and found out the ECM get's it's barometric pressure reading when it's at full throttle. So under boost at full throttle the baro measurement would become skewed and effect the rest of the fuel trims while normally driving. Unless that check valve will flow enough to counter-act it? What about hooking the vacuum feed for the MAP sensor up to a vacuum switching port. At full throttle the solenoid would switch the MAP sensor to a port that is just atmosphere pressure. That way baro measurement will be accurate. I'm just thinking out loud on this though.

As for fuel it runs roughly 50psi. Deadhead will shoot just over 100psi, but I know flow is more the issue. I figure the car is built to manage a little more than 2psi of boost added, since that would equal sea level. Another reason why I don't want to go up any much higher than 3-4psi. I'd rather stick with the stock fuel pump. Trying to keep this as budget build as possible!

This is also a MAF equipped engine. Looks like the sensor can read up to 320g/s roughly. At redline shifting I was only reading 155g/s so it looks like I have decent amount of room in regards to that sensor.

On the other side I finally tracked down a company in Canada that does tune these ECM's. But factor in their programming fee, a 2bar MAP sensor and bigger injectors and I'm already way over budget for just a fun commuter car. It would be awesome to crank it up more but it's still a Northstar with weak head gaskets and a front wheel drive transmission haha. The time-certs have already been done on it but just stock head bolts were used.

a "MAP clamp" is this.

http://www.6gc.net/forums/index.php?showtopic=75691&st=0&p=873758&#entry873758

the image at the beginning of the thread is what i made mine from. all parts from radio shack and cost me 6 bucks.

a check valve ran inline so the MAP sees no pressure when under boost but opens when under vaccum doesnt work well. i tried it. it will hold a little residual vac if you get off the throttle and hit fast straight to boost, which makes it go lean and fall on its face big time.

now running check valves so they open to atmosphere works though its kinda unsightly and its a boost leak. just dont use the cheap walmart fish tank ones, they dont like fuel and the plastic melts and plugs up (im a cheap ass too and they didnt work out lol). the other issue is you dont get to take full advange of the little extra fuel you can pull from the ECM via the MAP accurately this way.

the clamp soldiers into the three wires on the MAP sensor. what it does is when a certain voltage is met via the setting in the potentiometer, it bleeds voltage off to keep at that specific voltage down to .01v. you then adjust the potentiometer to where the voltage is "clamping" at and the ECM will never see a voltage higher than the setting. This lets you fine tune the ECM into giving you ever bit of fuel left in its fueling before it sees too much voltage and throws a check engine light. your higher altitude means you have a decent amount of fuel PW wise to gain from this. The ECM in my zuk will code at over 4.3v from the MAP. what it reads at baro is 3.8, that voltage difference there is the difference in 12.8AFR at 3.8v to 11.0AFR at 4.2v

the downside to the clamp is as you go down in elevation, you may see her leaning out some under boost as your basically going full primitive fueling at that point. its kinda the only way to do it unless you do stand alone additional injectors or tune the ecm.


as for the MAF, i dont have much info there for you. My zuk is MAP based and has no MAF.

you will need to figure out what your stock injectors flow and what around about flow you need to achieve the AFR you want at 3-4 psi. here is a good site for that, i use this one alot.
http://www.witchhunter.com/injectorcalc1.php

that will help you decide what ratio to put in the FMU and what you have room to play with as far as boost. its not 100% dead on but its close and gives a good base. Right now, im running a 8:1 kit in my FMU, so for every 1psi of boost, im increasing fuel pressure 8psi. they have kits ranging from 3:1 to 12:1. it seems most guys with sequential/batch fuel injection run 10:1 or 12:1 to get a good AFR.

Also, you will notice at partial throttle under boost when at a low rpm, it may run rich, its typical. i run a second cold start injector that switches on with a HOBBs switch to combat that and keep fuel mileage up as im constantly in boost on this little motor to keep me doing down the highway at 70mph. i doubt you will see a very rich condition with 3-4psi but just keep it in mind.

I also had a tech I work with donate a turbo that he ran on his Honda. Just one of those el-cheapo ebay special ones, but I figure if it blows I really don't care haha. It's a 60.5/68mm T3 SUPER T70.

nice!

does your car have a knock sensor?

 

[chevyburnout1]

That makes perfect sense! So the MAP clamp just limits the signal voltage back to the ECM once it hits a certain voltage so it doesn't set a MAP sensor high voltage code. So basically just set the limit a little higher than what my atmosphere voltage is, which showed 4.00v today. However I feel like if I just max out the MAP sensor limits the MAF sensor will fight it in it's fuel trim calculations and set a check engine light/go into default fueling. The MAF sensor is the main fuel control sensor from what I've seen/read. Most of the time the car stays at this elevation so it wouldn't be much of a problem. But I do venture up into the mountains and over Eisenhower pass a decent amount with it as well so being able to somewhat adjust automatically would be nice.

So how about this? I use that MAP clamp and then I install another MAP sensor on the firewall and tap into the 5volt/ground circuit from the original MAP sensor. Then rig up a full throttle switch and a relay. Run the stock MAP sensor signal output circuit to the '87a' (normally closed) terminal of the relay, then run the second MAP sensor output to the '87' (normally open) side of the relay. Full throttle will then switch from from the stock MAP sensor that's seeing boost pressure, to the secondary MAP sensor which is seeing atmospheric pressure. This way the baro measurements by the ECM will be correct. It's a theory!

Or I could just shut the engine off and restart it, as I believe it measured baro with key on as well.

The car does have a knock sensor and from the few and far between people I've found on Cadillac forums who are running turbo/nitrous setups it sounds like the ECM control for detonation is pretty legit and on top of things. So that, combined with low boost hopefully means no detonation issues.

I'll definitely look more into the fueling tonight after I get a few drinks in me haha. Running at 50psi doesn't give me much to rise up, however I have more injectors than you do so in theory bumping the pressure on my setup could ad a lot more fuel in relationship to your two injectors. But I guess the engine is larger in displacement so that may cancel out this theory.

 

[Chevy1925]

You have to remember, the MAF is going to see much more air flowing across it as well so the MAP set to its max should not affect what the MAF is doing. The clamp is what all the cheap ass Honda boys do when boosting their ricers and they all mostly have MAFs.

Doing the secondary MAP defeats the purpose of the clamp unless your saying there is a fourth wire that runs to the ecm to give Baro data although it seems weird it would use those values when at idle as it would be under vacuum. Keeping the MAP set only at atmospheric pressure limits your fueling and it may not play nice with the MAF. If you keep it just a touch off triggering the cel, your MAF and MAP should work together with the ecm just fine. But I'm only guessing. Only one way to find out!!

That's good cause having no knock sensor or a way to retard timing besides base timing sucks. Specially when your head bolts are weak and a little too much detonation pops it. I have to constantly listen when tuning it and inching boost up and I tell ya, it sucks. I put ARP headstuds in the little booger just to make sure the damn head stays clamped down!

Yeah your multiple injectors aren't much of a savior. My single stock 1.6 injector puts out 468 cc/min at 43.5psi and the cold start puts out 100cc/min. By the time I hit 80psi, I'm closing in on 800cc/min on that little motor. Your fuel pump and injectors will definitely be your limiter, specially if they are on the small side stock

 

[chevyburnout1]

The dual MAP setup would still be a three wire setup. The relay would decide which MAP sensor is sending the signal back to the ECM which is connected to the '30' terminal of the relay. So say I'm at 3/4 throttle, making boost, the ECM is not sampling for the baro yet. This is where the first sensor and the MAP clamp would still be needed for maximum utilization and to prevent the code from setting. Once under full throttle the ECM reads what the MAP sensor voltage is since an n/a engine will have atmosphere pressure in the intake with the throttle blades completely open. This is where the full throttle switch/relay will kick in and switch the signal output from the first MAP sensor to the second MAP sensor which is receiving atmosphere pressure, thus updating the ECM with the correct baro reading.

The reason I'm so concerned with making sure the baro updates correctly is in regards to normal everyday driving when the car is not on boost. I barely need much throttle for daily driving with how it runs n/a. I'm not sure if having the baro set at 4.xx will cause issues with normal daily driving. The ECM will expect 14.5-15psi of air pressure due to the fooled baro reading from the MAP, but the MAF sensor will be reading less air flow than calibrated for that baro pressure, which could possibly cause fuel trim numbers to be skewed far enough to the negative side that the ECM will code anyhow.

However! I may just be over thinking how much the MAP sensor really effects the ECM fuel trims and the MAP clamp may be all that is needed! I could build one of those clamps and try it out this weekend and see how the drivability/fuel trims look!

So I did a little research and it looks like my car has roughly 19-21.5lb injectors. Sounds like GM did their work at cranking out as much hp per gallon with these engines. That website you posted helped out a lot and was basically dead on with with the injectors flow rate based on the factory crank 275hp. So if I wanted to bump up to 375hp I would have to up the flow to 29.3lbs, which would mean I'd have to bump my fuel pressure to 93psi :spit: So I definitely think your right that my fuel system will be the limiter haha. I may be able to squeeze 350hp at 80psi fuel pressure but that will be pushing it! According to Garret's little boost advisor 350hp at my altitude will put me around 3.5psi of boost pressure. Sounds like a good start :happy2:

 

[Chevy1925]

Your over thinking the MAP. It doesn't care about where you physically are pressure wise in the atmosphere, the ECM just can't see a pressure beyond what it's programmed for. At sea level, that voltage may be 4.7v (some use 4.3v max and some use 4.7v max from what I read). So if you clamp at 4.65v when under boost yet atmosphere actually makes the map read 4.0v before the clamp, the computer is just going to think your next to sea level and fuel for that. So if that means it takes 2psi of boost to hit that 4.65v on the map,
That's how much pressure your short of reading atmospheric pressure at sea level. That's extra fuel you can take advantage of and really can make a difference. As long as you don't have a separate Baro sensor its trying to compare to, it should make no difference what the Baro samples at as long as you don't go beyond the threshold of what sets a code for it

Heck yeah that's a good start! Gunna make that car a lot of fun that's for sure!! Even though my motor is only makin about 130-140hp right now, it's like a fricken rocket compared to the 66hp it made before lol

 

[chevyburnout1]

Yeah I may be over thinking it too much haha. I'll build the clamp this weekend and see how the fuel trims deter with the car thinking it's at sea level. Hopefully the fuel trims still stay within ECM limits.

 

[chevyburnout1]

I'm bringing this back up again James! My truck will finally be back on the road this weekend so I'm planning on tearing into the car.

You were right, I thought too hard in regards to the MAP sensor, and the fuel system in general. It's a MAF car so all the calibrations for timing/fuel are calculated using the MAF. All the other sensors are just there for fuel trim calculations. The MAF sensor maxes out at about 40lbs/min and it's looking like I need about 32-34lbs/min of flow to reach my hp goal.

So in theory the ECM should have the calibrations to handle the extra airflow. I'm sure the calibrations are conservative, but it's good enough I'm sure to get it back on the road. Going to start rounding up some exhaust and tubing this weekend.

 

[Chevy1925]

I'm bringing this back up again James! My truck will finally be back on the road this weekend so I'm planning on tearing into the car.

You were right, I thought too hard in regards to the MAP sensor, and the fuel system in general. It's a MAF car so all the calibrations for timing/fuel are calculated using the MAF. All the other sensors are just there for fuel trim calculations. The MAF sensor maxes out at about 40lbs/min and it's looking like I need about 32-34lbs/min of flow to reach my hp goal.

So in theory the ECM should have the calibrations to handle the extra airflow. I'm sure the calibrations are conservative, but it's good enough I'm sure to get it back on the road. Going to start rounding up some exhaust and tubing this weekend.

awesome!! couple things you might have to look into is WOT enrichment. the computer may be set to only fuel to a targeted 13.0ish or so which is too lean for a turbo.

also, how many lbs/min is that motor ingesting as it is right now? you gotta remember that 32-34lbs/min is in addition to the amount the motor is sucking in as it is right now.

 

[chevyburnout1]

awesome!! couple things you might have to look into is WOT enrichment. the computer may be set to only fuel to a targeted 13.0ish or so which is too lean for a turbo.

also, how many lbs/min is that motor ingesting as it is right now? you gotta remember that 32-34lbs/min is in addition to the amount the motor is sucking in as it is right now.

So this first go around I'm not really looking to add any "additional power" over factory original. What I mean by that is I just want to make the engine think it is at sea level, which obviously the ECM should be perfectly happy in with fueling. So my location in Colorado now is 12.3psi atmo. So I figured a total of 3psi would work well to simulate sea level pressure and to compensate for the hotter air charge from the turbo with no intercooler. The MAF has an IAT sensor but I'm not sure how much it effects calibrations in this ECM.

I was originally saying a total of 32-34lbs/min will be needed for my max hp goal. For my first test though in theory I would only need about 28lbs/min of airflow to simulate sea level. Full throttle shifts at this altitude I'm reading about 20lbs/min from the MAF.

If/when I decide to up the horsepower over factory rated output will probably be when I have to start upping fuel pressure and fooling a few sensors.

 

[Chevy1925]

I got what your saying. No more posting though Dustin, just pics of the kit coming together! Lol