Marge

I know there is a lot of info on the supercharger out there but I have some specific questions regarding boost pulleys. I am doing a 3.4 swap into my 1991 pickup. I have been thinking about supercharging the engine if I can get hold of a supercharger relatively cheap. But I don't have the money for all the mods that people say are necessary for the supercharger on the 3.4 (URD fuel mod, 7th injector, etc.). I was wondering if I got a low PSI pulley (~7psi) would those modifications still be necessary? Or are they really necessary to begin with? I am a damn conservative driver, and I very rarely break 3000 rpm even during hard (for me) acceleration. For those of you who are questioning why I want the supercharger in the first place after my driving description, the answer is altitude driving and torque. I think the supercharger would help these aspects of driving but correct me if I am wrong.
Thanks,
Marge

neliconcept

you can try a 5 psi pulley and be conservative with your driving but later on you will still need to get the fuel upgrades, and the rest.

Maybe Midiwall will chime in.. Im not as knowledgable about this as he is as I dont even have an SC yet

montypower

I've had my SCr for close to 25k miles now. It has no fuel mods (factory boost pulley). Never pings. I live @ 300ft elevation. The truck has 156k miles now. Uses Zero oil. Idles perfectly smooth. Acceleration is awesome.

This is my experience. Others have had different results.

marko3xl3

Yeap, the stock pulley boost up to 6 psi at max. If you have a clean engine, you shouldn't ping if you go easy on it. The ECU retards the timing enough to prevent that. I live at 0ft-200ft of elevation and I have no problems at all. I often travel around 2000ft (Santa Cruz mountains) and I do not ping all the way through unless I get on it real hard.

So basically, if you want the S/C for torque and altitude, I would give the stock engine a try first and then get the S/C if you really need it, because you will definately need upgrades at high altitudes and if you are going to tow, your tranny won't last that long either.

Another option would be to get a larger pulley and then you would run into less problems or none at all.

rimpainter.com

Stock pulley is 6.5psi @ sea level. I hit 6.5 psi here @ 1100ft. Anyway, as you can see, a lot of us have had different experiences with supercharging. I always challenge the folks that say they have no audible ping to hook up an EGT guage and scan tool to get the true temps and AFR baseline. One should NEVER make a conclusion that everything is "ok" with no fuel/timing mods without hooking up the proper equipment to the engine. I speak from experience in saying this because I did it wrong at first too. When I finally did get things hooked up, I was shocked; EGTs were high, and the AFR trim was way off (25% too LEAN with stock injectors).

It is no secret that a stock 5VZ has a very hard time with forced induction. The stock injectors flow 238cc. In order to keep things in the safe zone, the injectors will be pushed 80% and above, which exceeds max duty cycle. In other words, it is extremely unsafe to operate the engine under boost in that zone for a sustained period of time. Equally concerning is how much the stock fuel pump can flow. It cannot flow enough fuel during sustained WOT runs (see passing, etc). I don't know about you, but that is not something I want to chance. If you don't believe me, take a look at the mods in my sig and then take a look at the timing matrix in my SMT 6 software...you will see 11 degrees of timing retard in places!

If you have any further questions, shoot. I have learned a lot by doing things the WRONG way and then making them right unfortunately.

marko3xl3

I corrected my post to say 6.5 psi. My boost gauge went a tiny bit above 6 at peak rpms and between 5-6 psi at lower rpm's but WOT.

You are also correct with everything else you said, but must you drive so aggresively without fuel mods? I don't think so. I have the S/C only right now (getting upgraded soon) and if I am easy on the pedal I can guarantee you that injector duty cycles and EGT temps will be just fine, which is the case here.

Ron(Fla)

I installed my SC at 25K, now have almost 70k and the only thing I have done is installed 2 step colder iridium plugs. Most of the miles were in Fla, but we now live in Tx and my GPS says 4K ft in the back yard. I haven't had any problems with pinging since I replaced the plugs. I also towed a ~2k lb u-haul from Fla to NJ. The boost stayed around 3lbs most of the trip with no pinging. My driving is also on the conservative side, and if I need to get on it I usually DS to 3rd, just like I did when I had my '80's Z cars.

My 4R is also towed behind a MH, so it has been driven under a lot of different conditions.

Just my experience......

rimpainter.com

You bring up a good point: driving style. I am an overly-aggressive driver. In fact, it's one of my downfalls; something that I have been working on for a while now. So, yeah, if you can go easy on the skinny and keep it out of boost, I don't think there is a big risk to your engine.

But there are times when any average Joe-Schmoe driver has to peg the skinny. Merging on the freeway between big rigs, passing, towing, going uphill loaded with gear on a camping trip or something...etc, etc. I used to cringe when I had to do that, now I smile . It's a much better feeling.

Ron jumped in and mentioned towing. Funny, because I bought a 97 with 197K miles on it, 100K of those miles were SC'd. And the rig was driven by a responsible older gent that towed a Harley from CA to ND. He also said it never had a problem and only experienced minimal pinging on rare occasions. Now I just knew that there was no way that scenario (no fuel/timing mods, towing, etc) couldn't have done anything. Well, when I was finally able to crawl under the rig when I got it home, I discovered I was right. The EGT's must have been so high that the heat shields around the crossover pipes of the exhaust manifolds had been melted in places. It was the craziest thing I had ever seen. We are dealing with an extremely durable engine here guys, which is exactly why we have only seen a handfull of catastrophic engine failures with the SC'r and no fuel mods. I hope it never happens to any of us. Now, if I could just drive more like a grandpa...

marko3xl3

We are very similar then. And your reason is the same reason I am going with an upgrade soon.

MTL_4runner

Yeah, right......there's just too many fart can ricers ripe for the picking out in Phoenix.

One way to possibly drive with just the S/C would be to add a much larger pulley to severely limit the boost (more like 2-2.5 psi max not 7 psi which is on the high side of what a standard S/C would make). This would push the injector duty quite high for the stock setup, but it may keep EGTs cool enough to prevent pinging (provided you're using 91+ octane) even under load (such as up steep grades or while towing). The downside is that you're also severly castrating the benefit of the S/C in the first place so the amount of additional HP and torque will be heavily downgraded as well (you might only make 1/3-1/2 the typical S/C benefits). This is why most people would be wise to just do the fuel mods when running a S/C on the 5VZ.

Ron(Fla)

I guess I have just been lucky, or maybe it's my driving style... When I clean the under-carriage I haven't seen any sign of over-heating. In fact, up untill last year when I spent 3 months in BC visiting my son, the exhaust was very clean. He lives in a mountain valley, 2500 ft, on a logging road. I don't think it will ever be clean again.

Marge

Wow, thanks for the info guys! Sounds like I am better off just leaving it stock until I can scare up enough money to do it right. I want reliability more than performance as money can be scarce for a 26 year old.
Thanks guys,
Marge

SEAN_at_TLT

Just wait until you get teh 3.4 in there, you'll be very happy with the added power w/o any supercharger. If after a year or so you think you need it then add it and do it right with URD/IPT etc....

Marge

Yep, so far stoked with the 3.4L. I am leaving it super-charger free for the moment. I will be driving cross-country to Alabama this Fall so crossing the Sierra Nevada and Rockies will be a great test.

Thanks for all the info,
Mario

NaeSLaS

rule of thumb that i've heard all the time:

before making car faster, first make brakes better.
before adding boost, make the car able to handle it first.