supercharging, map sensors and MSD BTM questions

[bdep73]

ok guys I need some help understanding boost and map sensors with a stock ecu. I bought a novi 2000 8 -10 lb kit for my 1990 mustang. originally I was going to do it the right way by getting Andersons PMS and larger injectors and not using the fmu that came with the kit but money is going to be a little tight for awhile. So spending $1000 for the pms $400 for injectors and $100 to have my Pro-M calibrated to the larger injectors is just not an option this summer. so until i can get that stuff for now to save money I am going to use the fmu with my 24lb injectors and buy a msd boost timing master to add to my msd 6al for $250 and be done with it. the issue is this the msd BTM should be hooked up to a map sensor, and it is my understanding that to run 8 - 10lbs of boost I would need to run a 3 bar map sensor but the stock map sensor for my car I believe is a two bar because N/A cars only need a 2 bar map sensor. now everybody says that your cars ecu has to be calibrated to run a 3 bar map sensor because if it's not the ecu wont recognize the additional bar of boost and therfore won't send the required amount of fuel and lean out your engine. I thought if you ran the fmu that came with the kit and a boost timing master you wont need to tune your computer but how will the msd btm know to retard my timing if its getting its readings form a 2 bar map sensor which isnt recognizing the full amount of boost.
Am I over thinking this I would really appreciate some help understanding all this Thanks.

 

[Noobz347]

Your ECU in it's current form WILL NOT understand a boost reading from ANY MAP sensor, period.

You do NOT need to recalibrate your mass air meter for ANY size injectors if you tune it by either a PMS or other digital means. What you need is the transfer function that came with your meter when you bought it so that these flow voltages can be input into whatever tuning media you end up using.

Unless you're running an AFR meter or have some way to read your air/fuel ratio as you're setting this MSD ignition retard up, then you're spinning your wheels. It's a near useless exercise in futility because you have no way of knowing (other than listening for detonation (bad idea as detonation occurs before you can actually hear it)) of knowing whether you have it configured/setup correctly.

You say you're running 24lb injectors.... what fuel pump are you running? What is the ratio of the diaphragm inside of the FMU? Is it the correct one? If it's the 10:1 diaphragm common in most 87+ Mustang kits, then you'll be running pig rich through the entire power band once boost and the FMU kick in with 24lb injectors.

Here's my advice for your current situation:

STOP WHAT YOU'RE DOING! The description you've just provided is usually followed by a thread about blown head gaskets or motor.

Money is an issue, I get it. Install your supercharger, and take it to a dyno tuner. Yes... take your FMU and use your current injectors (for now). Let a professional tune it. I means buying a chip and dyno time and possibly a replacement diaphragm for your FMU but it will hold you over until you're able to afford injectors.

You do not need the MSD box at all. Close your spark gap to .034 and let the tuner add/subtract ignition timing based on what it needs and based on an initial timing of 10*.

This way, you'll save some money now and not be back with a horror story about a blown motor.

Later, once you have the injectors and other supporting mods, you'll only need to pay for the new tune and dyno-time (you reuse the same chip).

 

[Blown88GT]

Use what came with the kit, it will work. When these things were developed 20 years ago, there were no dynos & no tuners, no Tweecers, etc. Prochargers were getting over 400hp on pump gas with 19lb injectors & doing the 1/4 in the low 12's, on a completely stock engine. This is now considered "old school", but that doesn't mean it doesn't work.

FMU's & MAF's are calibrated for the injectors you have. You will need a boost pump if your in-tank is not up to the task. MAP sensor has nothing to do with it. I assume you already have the MAF working with the 24 lb injectors? Since you don't have an intercooler, you will probably need some boost retard. Don't know if the MSD 6AL has this feature. Sufficient fuel at boost is the primary consideration.

 

[Noobz347]

The only problem is that what came with the kit was intended for an OEM install. He says he's running 24s.

 

[bdep73]

first off thanks for responding let me start by saying I am well aware of everything you have said the only thing i didnt know was that I did not have to have my pmas recalibrated if i use a PMS. the reason their is some confusion is Vortech's S-trim complete kit for my car comes with a T-rex external pump (which I already have on the car) A fmu (I have the 8:1 disc for my 24's) and a MSD BTM and Vortech claims that is all you need to run that kit. granted I got the novi 2000 kit which comes with similar stuff but 8 -10 lbs is 8- 10lbs so its the same basic idea. so why does vortech sell that as a complete kit if I have to have a chip and dyno tuning done which where i live will cost more than buying the pms so thats out. the whole reason I started this thread is because MSD says to T in to the boost port of my boost gauge if I have one and Autometers boost gauge comes with a map sensor so if my car won't recognize the map sensor then Vortech or Paxtons complete kit ir far from complete and I wanted to make sure I was not overlooking something. Also you asked what fuel pumps I have I have the Vortech T-rex external and a 190lph in tank.

 

[bdep73]

Use what came with the kit, it will work. When these things were developed 20 years ago, there were no dynos & no tuners, no Tweecers, etc. Prochargers were getting over 400hp on pump gas with 19lb injectors & doing the 1/4 in the low 12's, on a completely stock engine. This is now considered "old school", but that doesn't mean it doesn't work.

FMU's & MAF's are calibrated for the injectors you have. You will need a boost pump if your in-tank is not up to the task. MAP sensor has nothing to do with it. I assume you already have the MAF working with the 24 lb injectors? Since you don't have an intercooler, you will probably need some boost retard. Don't know if the MSD 6AL has this feature. Sufficient fuel at boost is the primary consideration.

Thank you this is what I hoping that I can use the kit as is untill I can afford a pms or other form of proper tuning. the MSD 6aAL does not have the boost retard feature but for $250 i can add the boost timing master to the 6AL

 

[Noobz347]

The EEC should see the MAP sensor just fine. What it WON'T see is the boost. The MSD BTM will though. It was designed to.

One other problem that I see with your setup is the 190lph in-tank fuel pump. The Walboro 190L pumps have a tendency to internally by-pass at around 60psi. Your FMU will crank fuel pressures to WELL ABOVE 60 psi when you're in boost.

Be mindful of that because I'm not 100% certain that the T-rex will make up that difference when the in-tank by-passes. It SHOULD so long as it continues to get fuel but if fuel delivery stops at the in-tank pump, then *poof*.

 

[bdep73]

The EEC should see the MAP sensor just fine. What it WON'T see is the boost. The MSD BTM will though. It was designed to.

One other problem that I see with your setup is the 190lph in-tank fuel pump. The Walboro 190L pumps have a tendency to internally by-pass at around 60psi. Your FMU will crank fuel pressures to WELL ABOVE 60 psi when you're in boost.

Be mindful of that because I'm not 100% certain that the T-rex will make up that difference when the in-tank by-passes. It SHOULD so long as it continues to get fuel but if fuel delivery stops at the in-tank pump, then *poof*.

Thank you that acually cleared everything up for me and you have definitely set my mind at ease. I am gald you mentioned the in tank pump because i was worried about that myself. do you think it would be better to drop $120 or so and get a 255lph

 

[Noobz347]

I fit were me, I would replace it with a 255 HP (high pressure) and not leave it to chance.

Something else occurred to me as I was sitting here eating my pizza. Take the MAP sensor that you intend to use and install it in the car. Run it for a while then pull codes. That will tell you 100% whether your EEC has any problem whatsoever with that MAP.

Be very careful about detonation my friend. I'm a bit more OCD than most and I'd never install a blower on a motor without some way to verify the AFR under boost.

 

[Noobz347]

post above edited to indicate high pressure 255 vs. regular 255. Important for boosted apps. Even more important for boosted apps using an FMU.

 

[bdep73]

I fit were me, I would replace it with a 255 and not leave it to chance.

Something else occurred to me as I was sitting here eating my pizza. Take the MAP sensor that you intend to use and install it in the car. Run it for a while then pull codes. That will tell you 100% whether your EEC has any problem whatsoever with that MAP.

Be very careful about detonation my friend. I'm a bit more OCD than most and I'd never install a blower on a motor without some way to verify the AFR under boost.

I totally hear what you are saying and based on that I may wait a few more weeks and a least get a wideband I've seen them for like 200 bucks. I just being a little impatient i want to get it in the car asap but you are right on with your advice and I appreciate it.

 

[bdep73]

post above edited to indicate high pressure 255 vs. regular 255. Important for boosted apps. Even more important for boosted apps using an FMU.

I have seen them both and I didn't realize there was a difference. you just saved me a wrong buy and a return.

 

[Noobz347]

I totally hear what you are saying and based on that I may wait a few more weeks and a least get a wideband I've seen them for like 200 bucks. I just being a little impatient i want to get it in the car asap but you are right on with your advice and I appreciate it.

IMO... that would be a VERY wise move. At least then you'll have the ability to see if there's a problem before there's damage.