Category:94-95 Mustangs Poweradders Superchargers
From Mustang-Tech
Contents |
Overview
A supercharger's job is to force more air into the engine. The more air that's stuffed in, the more fuel you can use, and the more power you can get out of an engine. Superchargers require a belt to drive them and thus create a certain degree of parasitic loss. Also, by compressing the air the supercharger can put out some very warm air, which isn't very good for performance. This is why most people use inter/aftercooler setups as well as meth/water injection. Some people also use a small shot of nitrous to cool the intake charge. Considering atmospheric pressure is at 14.7 PSI at sea level, if a supercharger is putting out 7-8 lbs of boost, that is stuffing 50% more air into the engine (in a perfect world). It actually comes out to aprox. 35% or so more. Also, a supercharger can increase gas mileage my improving efficiency.
Vendors
General Safety
Superchargers are generally very safe (unless one happens to shoot stuff at you). The main things to avoid are common sense kind of things such as getting close to the belt or touching it as superchargers generate a good deal of heat.
Before You Begin
You'll want to make sure that your engine is in great mechanical condition. I'd recommend a leakdown/compression test. Test for any vacuum leaks and make sure your fuel system is up to par. You'll want to run plugs that are 2 degrees colder and gapped at ~.032. You'll also want an aftermarket ignition box and coil to prevent spark blowout. I would only use a band-aid (such as vortech's FMU) to get me to a tuner...I've found that they can be unreliable. Set some money aside for a higher flowing fuel pump, at least 42 lb/hr injectors, and a matching maf. Nothing's worse than running out of injector/pump at 5500+ rpm..instant lean condition...and instant blown headgasket (hopefully only the headgasket)
Non-twEECer Tuning
When running the average of 8-10 PSI, I've found that the best place to start off at is backing the timing down by 2 degrees initial. Run 93 octane (or highest available) and see if you hear any pinging...at the slightest bit BACK OFF...pinging and forced induction don't go together very well and will pop a headgasket in no time. After that, I would slowly knock it up a bit to try and optimize the timing. Again, don't get too happy, it doesn't take long to screw something up.
twEECer Tuning
I've found that the safest A/F ratio to run is 11.5 to 12.00:1. I would not go any higher than this unless you like living on the ragged edge. It's best to get your A/F to a safe ratio, and then up your spark from there while keeping a constant eye on the A/F. I've found that a good starting place for timing is around 18* total timing (with 10 initial). You can then work your way up from there. BIG fuel, LITTLE spark is the best way to start off...especially if you're unsure about what your combo likes. With a centrifugal supercharger, I would up my high-load, low rpm timing until the performance gains stop....and then once the boost starts kicking in (around 3000 rpm or so) I'd start dropping that number down to whatever total timing works best for your combo. I don't have much experience with kenne bells so maybe someone can add?
Spark Retard via ACT (ACT AFTER the blower)
From Mike Glover: [1]
On intercooled (including meth inj) boosted applications, I start removing 6deg @ 180degf. this gives some retard before 180, as the eec uses 4pt interpolation and is weighted as it approaches the value or is in between values. ie if there is -4 @ 180 and -10 @ 200 then there should be -7 @ 190.
This is still the best method (without spending $$ on a hardware solution) to implement a spark retard. I generally tune a 5-6psi setup as a high compression NA setup (obviously adjusting even more if it is high compression), at that point I start limiting spark at least 1deg per psi above that.
The following are MY general starting points, no science to it, just tuning experience.
Assuming stock level compression (8.75-9.25):
- 8-10psi will see a max of 26deg @ wot
- 11-14psi will see a max of 23deg @ wot
- Start removing 1.5deg per psi above 14psi.
My turbo setup is @ 8.25:1 and sees 29deg @ wot with 93octane.
Common Problems
Breaking up past 5000 rpms
Whenever there is a power cut-off after 5000 rpms, I've found that it is usually spark blowout. The increase in cylinder pressure blows the spark out before it can properly ignite the mixture. Fixes can be: gapping plugs to .032 or so degrees, aftermarket ignition box, aftermarket ignition coil.
Detonation
Generally pinging is caused by running to much total timing. Backing off on the timing can stop the detonation. Running a richer A/F ratio can also stave off detonation. Another cause can be running sparkplugs that aren't cold enough for the blower...generally 2 degrees colder is the way to go.
Low boost numbers
The most common cause of this is a slipping belt. Either tighten it up or get a tighter belt. Another cause can be a restricted intake tract (pre-blower). This is why powerpipes allow extra boost...they can flow more air in. Also, check for any leaks.
How come my same setup doesn't put out as much boost as his
Boost numbers are kind of like peak dyno numbers. If you have a combo that flows a lot of air, you'll put out less boost than someone that has a stock combo. Restrictions after the blower increase PSI, and vice versa. Restrictions pre-blower reduce PSI, and vice versa. Think of it like this...you have two straws, one is huge and one is tiny in diameter. Let's say you blow with the same air pressure through each straw using one full breath of air. Which one makes you run out of breath sooner? The same applies with FI and engine restrictions...you'll see higher boost numbers on a stock engine because there's more pressure in the intake manifold ....but, slap the same setup on an H/C/I combo and you'll see less boost...since that air isn't getting backed up...and the one with less boost will actually make more power.
PCV/dipstick popping out under boost
Basically, your crankcase is being pressurized..either by a faulty pcv valve or by excessive blow by. What I found works very well for me is using a supercoupe PCV valve (EV127A part number), new PCV screen, and new rubber grommit that I used a bit of RTV on so it'd stay in the hole. I also got an oil separater (steeda part). I did this and had no more problems. Also, if none of that works (something I eventually did as well), you could change out your oil dipstick in favor of one that has an O-ring on it.
See Also: 94-95_Mustangs_Engine_PCV
How do I get more power out of my supercharger
Simple. All you have to do is change the pulley to a smaller pulley and it'll spin the blower faster. I've found that on vortech's, 2.95 is the lowest you can go without getting a lot of belt slippage. Also, you can buy a tensioner piece so you can manually tighten your belt down. One could also change the crank pulley. Basically, you'll see a 1-2 PSI boost increase for each pulley size smaller you go. One PSI generally equals out to roughly 10 hp.
I have a Vortech, and can't get an aftercooler to fit
There have been some people that have flipped an aftermarket intake manifold and fabbed up some pipe to get one to fit. If you don't wanna go through that...Snow Performance makes an excellent boost cooler. It reduces discharge temps and effectively raises the octane rating of your gas. It allows you to run more timing (10 more degrees safely in my case). One degree of timing is worth roughly 4hp...so you figure I gained 40HP out of timing, and I also upped the boost by 2 pulley sizes which upped it around 35hp...this was all on a very safe tune. I'll take 75+hp any day of the week.
Feel free to contact Cbarr300 and let me know of any changes/additions that should be made
Notes
This category currently contains no articles or media.
