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Old 07-02-2019, 12:56 PM   #51
stevieturbo
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too high CR will limit timing, not allow it.

Depends how good your base fuel is. Depends how much water/meth you intend to use. There are lots of variables.

But with good tuning and sensible charge temps, given the nature of a centri, 9.5:1! does not sound unreasonable.
Although being cautious and if it's on pump, I'd still be inclined to aim a little lower.
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Old 07-02-2019, 02:55 PM   #52
pcampbell
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Yeah best Iíll get is 93 plus water meth. I have no problem using a big fat injection of 50/50. But with the SC canít necessarily just add more boost if you go too low CR to start.
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Old 07-10-2019, 07:00 AM   #53
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Default Vortech supercharger for ~500whp? Si Too big?

Here is the latest 13ish psi semi custom pulley. Itís smaller than the smallest Vortech you can buy.

People on other forums were concerned about how close the belt is to itself but Iím not seeing any issues.

Some timing tuning and then will get on the dyno. Maf sensor hit 325 g/s and it should go up with some tuning but I donít know how accurate the MAF scaling is. AFR and injector duty is in the right spot roughly though.

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Old 07-10-2019, 12:45 PM   #54
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Any wobble at all...and there will be some and those belts could well touch.

I would be inclined to want to move that lower idler down a little.
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Old 07-10-2019, 07:44 PM   #55
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Dayco 89535 is half way in between the diameter of the upper and lower pulley. Might be an easy way to get that extra gap with very little effort!
(Removing the plate to redrill is a PITA!)
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Old 07-13-2019, 09:07 AM   #56
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I ordered that smaller Dayco. I will move the big idler next to the crank pulley for more crank pulley wrap.

I finally got a dyno date for the Super EJ253. MAF is reading over 360 g/s at 6400rpm and AFR is high 10s (including water meth), just under 14psi, ~20 deg timing. Hard to know how accurate that is or what it might mean for AWHP. If g/s ~= WHP but we lose 15% to the Supercharger then roughly 360*.85 it's only just barely over 300whp which is kind of lame but I think maybe realistic...

Last edited by pcampbell; 07-13-2019 at 09:17 AM.
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Old 07-13-2019, 09:28 AM   #57
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Possible projection of crank hp

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Old 07-13-2019, 01:40 PM   #58
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My whp was about 10% higher than MAF, so you could be well over 300. It depends on lots of stuff though, especially injector scaling.
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Old 07-13-2019, 02:04 PM   #59
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I calculate 41 hp for the supercharger at 75% efficiency, so maybe 320 whp? You have no backpressure from a turbine, so cylinder filling will be a little better.

BTW, how high does that MAF read?
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Old 07-14-2019, 08:17 AM   #60
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Default Vortech supercharger for ~500whp? Si Too big?

Thanks.. the MAF scaling is bizarre when it gets up to the top end, but there are a few variables at play. It is an aftermarket 3" OD but roughly 2.75" ID with honeycomb air straightener, it is also an aftermarket MAF sensor (I dropped the stock one and wasn't sure it was reliable anymore and had an aftermarket sitting on the shelf so I went with it).

I would say it's questionable but the wideband sort of checks it out in the sense that the wideband AFR is close to the target AFR + water meth injection.

Here is the stock (left) vs new (right) maf scaling. It looks roughly normal--slightly more than stock--until 4.22v then it's grossly more than stock. I've only hit up to 4.3v on the road.



I have never hit 4.34, 4.45 or 4.57 . It is also possible (????) maybe that my fuel pump (new but stock flow for an Outback XT) can't keep up after ~4.06v so I am disproportionately scaling UP the MAF to get it to fuel correctly (????). I know we're roughly on the line with a stock 40-50gph fuel pump. Maybe a new fuel pump in the near future....
The more I think about it , itís got to be the only logical explanation, so itís probably not really 360 g/s lol.

Seems like itíd be worth trying before dyno.

Other random thought. Think the 40gph should be good for a solid 300whp if not a little more so Iím not quite sure what to think.

Last edited by pcampbell; 07-14-2019 at 12:51 PM.
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Old 07-15-2019, 02:23 PM   #61
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Ordered a Cobb 255 pump, let's see how it goes.
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Old 07-15-2019, 10:51 PM   #62
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Given the shape of the MAF curve, I think your failing-fuel-pump theory is promising.
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Old 07-16-2019, 07:33 AM   #63
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Default Vortech supercharger for ~500whp? Si Too big?

Yeah I should have realized this earlier. For some reason I though the stocker XT pump would do better. But seems like itíd run out around 300whp. +/- some depending on afr etc. Thatís one less thing Iíll have to do if I go bigger !

Last edited by pcampbell; 07-16-2019 at 07:46 AM.
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Old 07-16-2019, 09:33 AM   #64
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Slightly smaller idler pulley on the SC - gives a little more belt to belt clearance. I took up the slack by adding bigger idler pulley to crank for more crank pulley wrap.

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Old 07-16-2019, 10:35 AM   #65
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I am thinking about some way to get ambient temp air to the intake. Right now I am losing like +20 if not +30 F just to the intake filter location, real dumb. I am pondering a boxed in intake around the filter with a functional hood scoop which is sealed via rubber along the top of the box (sort of like stock TMIC).
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Old 07-24-2019, 03:19 PM   #66
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Just a thought. My MAF sensor tables on my ROM end at 4.57 volts. Is there any reason I can't steal some rows from the bottom end to plot it out up closer to 5 volts in the future? The sensor is the same as on a 2005 STI.
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Old 07-24-2019, 08:36 PM   #67
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Perhaps obvious, but you spend a whole lot more time below 40 g/s than you do at 350 g/s, so the better curve fit down low provides better fueling where needed. That said, if you accept that loss, you could add more points in the 4+ V region, but what are you going to fit against? When I tune a MAF, I use thousands of data points to average out an errors in measurement, fueling models, etc. In this case, I think you are going to have a reasonably limited number of data points during pulls from the WBO2. It'll work, just know the limitations.
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Old 07-25-2019, 07:00 AM   #68
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Default Vortech supercharger for ~500whp? Si Too big?

I was thinking of stealing rows between key off, say 0.7v and and low idle(?), say 1.2v. Not sure if those data points matters enough to affect how it starts up.
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Old 07-27-2019, 03:48 PM   #69
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Default Vortech supercharger for ~500whp? Si Too big?

For my budget build should I do stock sti rods with ARP bolts or cheap $325-350 Eagle or K1 rods. If buying new they will both cost $350 total at most. The eagles or k1 also come with ARP bolts. I will plan on using Manley pistons in whatever dish yields an appropriate CR in the 9:1 range. I have to measure the stock pistons first.
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Old 07-28-2019, 11:21 PM   #70
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Not sure about your ROM, but mine lets you enter whatever numbers you want in the voltage column. If yours is similar, you don't really need to steal rows, you can just use larger intervals between rows.

If you have Excel, plot the curve and eyeball it as a sanity check.
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Old 07-30-2019, 07:45 AM   #71
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Yeah same idea. I donít know that I actually will need to but nice to know I can do that before starting over with a new maf tube etc.
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Old 08-03-2019, 07:48 AM   #72
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Default Vortech supercharger for ~500whp? Si Too big?

Now Iím dealing with a misfire at 5500 plus only under heavy boost.

Changed plugs, coil and wire and plug gap (smaller) to no avail.

Iím going to try to improve the rusty grounding straps and pray.

If that doesnít work I will change injectors then Iím out of ideas.

Itís not a bad misfire. Like 4 count. But itís consistent and only on cyl 1.

My dyno day is Wednesday and really would love it firing all 4 on the dyno.

Iíve literally read of people having misfires specifically at 5500 plus and specifically under boost and it ended up being a ground problem. I donít know if thatíd be an injector or plug ground. Could the plug threads in the head be so dirty itís not getting a ground ?

Certainly could drive one nuts!!!!
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Old 08-04-2019, 02:58 PM   #73
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Make sure the engine's ground strap is (or straps are) connected solidly at both ends. It's hard to believe ground issues would only manifest at high RPM though... My only ground issues were so bad that the engine wouldn't even idle - I had that happen once with my Subaru (my mistake) and once with a C5 (shop's mistake).
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Old 08-07-2019, 07:38 AM   #74
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I added 4 new quality strap grounds and wire wheeled the body and motor part at attachment point. 1 on each side of the intake and 1 under each head. Itís still misfiring 1 or 2 or 3 counts on cylinder 1. Iíve also leaned out the water meth injection thinking itís maybe too thick. Anyway Iím off to the dyno this morning so will tinker with it more later.
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Old 08-07-2019, 02:39 PM   #75
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Hit up the dyno this morning, numbers are OK but it is still misfiring (and misfiring more when I add ignition timi,ng), I feel like there is definitely room to gain a bit once I get this issue fixed. Torque seems oddly low compared to HP for a torquey SOHC 10:1 motor.

259 hp @ 6150rpm
225 lb ft @ 5600rpm

The tuner suggested that I try adding fuel to cylinder 1 through per injector primary fuel offset compensation to try to resolve the misfire. I want to check injector blueprints to see if injector #1 was the one with the least flow also.



Timing is a little choppier.


More work to be done...

Last edited by pcampbell; 08-07-2019 at 03:47 PM.
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