Andrew & Tamra's 818SR EM Autox Hybrid Destroked Long-Rod Build

[Mechie3]

To be honest, we have no idea and we thought that they did function the same. However, the tuner was having a hard time even tuning the idle before he realized that it was a BPV that was being used as a BOV. Once he figured that out and switched to speed density, it was smooth sailing.

I believe that there would be a difference when tuning. The BPV and BOV serve the same purpose, but the BPV directs the released air back into the intake before the turbo and after the MAF. There would definitely be a difference in the readings of the MAF in the two different scenarios, which may require some changes in the tune.

I get that part, but that brings up several questions. Why did it have trouble just idling? Most tuners tune in a single gear, they aren't tuning across a shift point so during a pull the BPV/BOV shouldn't be dumping air so they wouldn't even see that effect. Many manufacturers sell a BOV that can be made into a BPV by adding a recirc tube. Mechanically all BPV/BOV are a piston with a spring, a boost reference port, an inlet and an outlet.

The only thing I can think of is that the spring isn't strong enough under vacuum to remain closed and it requires some amount of vacuum from the recirc hose to pull the piston down in order to maintain a seal. Seems a bit unlikely. Either way, it means they had a pretty bad air leak somewhere if it required speed density to fix. Perhaps under boost it didn't matter and speed density was required only to allow it to idle as under boost it would be held shut by pressure on the boost reference port.

[Tamra]

I guess I will have to pry it out of you as to the gauge brand... What and where did you get them? The features "sound" interesting.

Oh sorry about that - i thought we mentioned them somewhere. They are all Prosport gauges. Economically priced, and seem pretty accurate. We read that they have some issues with sensors going out sometimes, but as long as they are working they are accurate. We checked our oil pressure gauge accuracy using an STRI gauge that we had for another car, and they matched. The alarm function is nice, although annoying because our oil pressure gauge starts sounding as soon as the key is turned to the "on" position lol. It's a race car though!

I get that part, but that brings up several questions. Why did it have trouble just idling? Most tuners tune in a single gear, they aren't tuning across a shift point so during a pull the BPV/BOV shouldn't be dumping air so they wouldn't even see that effect. Many manufacturers sell a BOV that can be made into a BPV by adding a recirc tube. Mechanically all BPV/BOV are a piston with a spring, a boost reference port, an inlet and an outlet.

The only thing I can think of is that the spring isn't strong enough under vacuum to remain closed and it requires some amount of vacuum from the recirc hose to pull the piston down in order to maintain a seal. Seems a bit unlikely. Either way, it means they had a pretty bad air leak somewhere if it required speed density to fix. Perhaps under boost it didn't matter and speed density was required only to allow it to idle as under boost it would be held shut by pressure on the boost reference port.

I think that could be a possibility, but I haven't taken the time to try to research it much. Initially we didn't have boost running to it and the car idled fine, but as soon as we hooked up the final hoses the car was not happy. EFI Logics and their tuner STI Mikey are well known as one of the best tuning shops on the East Coast, so our car was in good hands and they got it sorted out with a nice safe tune. With everything going on (the car was on the dyno for over 2 hours, and had 23km of dyno runs), we didn't ask too many details on why the Forge caused the problem - all I know is that they worked around it and got a solid tune on the car.

[Mechie3]

I was tuned by EFI back in the day when they were at XX tuning and run by Chris. I don't doubt their skills. I tried researching it and all I found was "BPV vs BOV" with no results on using a BPV as a BOV. I'm just curious to know why something happened so it can be understood vs a simple "don't do this". lol.

[xxguitarist]

I'll ask today alongside requesting the electronic copy of the plots.

[Aero STI]

The sealing surface of a BPV is generally very small, whereas a BOV has a huge moving piston that creates a large amount of sealing surface. Without the plumb back the BPV will leak to atmosphere at idle/low boost.

Subaru BPV


Random BOV


Hybrid BOV

[Mechie3]

Thanks for that info. I'm a little confused on the diagrams though as they don't show the boost reference port on top. Under low boost the underside of the piston should see vacuum which would help pull it shut, though if the surface area on the back side is larger it would pull it back open. It's good info to file away though.

[xxguitarist]

We got the Dyno plot today, and a little clarification on the BOV/BPV thing, but I suspect that Aero explained it better, and I'm a bit confused still.. so.. graph!

It's not the highest peak number we saw at that boost level, but still shows the shape of the curves.

[Mitch Wright]

That looks like a great package for Autocrossing and peak power isn't dropping off much at 7000.

[Hindsight]

Very nice!

[Mechie3]

Torque curve looks great!

[Tamra]

Thanks guys! We aren't even concerned about maintaining power to redline, although we were impressed at how well it held it. We are mostly wanting to avoid shifting on the autox course as much as we can - basically stretch 2nd gear a little further, even if the power drops off. It's an added bonus that it's holding it pretty well with only about 1psi of boost loss in the high rpms.

Mikey said the speedo was burying itself in 3rd gear (cluster goes to 180kph). The video we took looks like it exceeded 100mph by a little at 7300rpm, and I think the final red line was 7500. Our goal is to stretch 2nd gear as far as possible, so that number remains to be seen. Our red line will also be increased later, but we kept things a little tame for now.

[tebriel]

Tamra/Andrew(Tamdrew?) - with the car idling just stick your hand over the outlet on the BOV/BPV - if there's suction it's leaking at idle and will cause issues tuning with MAF. Speed density doesn't care about that though. Are you using the stock ECU? Can't remember

[xxguitarist]

Tebriel, We'll give that a try next time it's running. Makes sense. I guess I just assumed it should be sealed..

Yes, we're on the stock 02 ECU, with a Cobb AP for flashing.

[Aero STI]

The graph looks great.

Mikey e-tuned my blue Saabaru and one of my WRXs. He road tuned my silver Saabaru in person. You can't go wrong with him.

I may use his "tri-state tuning rival", Junior, for the 818, but only out of convenience (he tunes at P&L from time to time).

[Hindsight]

I am having trouble finding a water temp gauge that will measure temps below 100F. Does your AWIC gauge go below 100 and if so, what is the brand? Thanks!

[xxguitarist]

Hindsight,
We are running up against the same issue.

I didn't realize it until we were installing them in the dash.
I'm suspicious that ProSport's digital might, but not sure, and can't get them to confirm or categorically deny it.

[Mechie3]

Prosport doesn't make their own gauges. I think they're made by race line? I'll have to look it up again. I found the generic version of the prosport guage for 1/2 the cost of the prosport. It just says the mfg name instead of prosport. Unfortunately the mfg's website is Engrish and not very good for data.

[Harley818]

Mechie, I'd be keen to know who you bought yours from. I'm in the process of selection now.
Found lots of Prosport gauges in China, but who knows if they are the same manufacturer.
Yours are good so far?

[Tamra]

We bought ours from Mike and Builtej.com. He got us an excellent price (really, he has excellent prices on all aftermarket Subaru parts) and no problems with the gauges so far.

[metros]

I'm using spa dual gauges. I've used them in a turbo s2000 in the past and thought they read water temp below 100*f. You'd have to check to be sure as it has been a few years. They're also digital.

[Hindsight]

Thanks Tamra. I've been leaning toward the Pro-Sports overall. My only issue is that I'd like to have all my gauges matching if possible, while also having idiot buzzers. That combination is tough to find. Their dual digital boost temp gauge only appears to come in blue.

Speaking of gauges, in my browsing I came across Defi brand which seems to be popular with the Subaru community. $240 a gauge!!!!

[Mechie3]

Defi are nice, but more of a fashion statement nowadays to an extent. Kind of like legit wheels vs rotas. Rotas are 90% as good in most situations.

The company is Race Tech. It says the gauge does 0-300F, but no comments on accuracy over that range. They don't claim to make prosports, but the gauges look identical. I can't find the race tech site directly, but when I had it said that their products are sold something like 20% as their own name and 80% rebranded for customers. They also make Dragon Gauge IIRC.

http://www.car-lab.com/search.php?se...ry=intercooler

http://www.ebay.com/itm/52mm-Dual-Ai...659c0f&vxp=mtr

My luck with prosports has been mostly good. I did have an oil pressure sender go bad, but it was cheap to replace.

[Hindsight]

Nice, thanks for that info Mechie. Will save some money.

[Tamra]

This weekend we worked on finishing up loose ends in prep for our autocross next Sunday.

We relocated the harness bar tabs on the roll bar to get the angle that Schroth recommended for the harnesses. The FFR location was too high, and the chassis tube was too low. We moved them down about 1". Photo is pre-paint so you can see it better.



Also welded on a tab for the submarine seat belt to bolt to:


Installed:


We also installed the firewall permanently:


Seats are permanently installed on their sliders. We drilled additional holes in order to tip them back and get them lower. We also installed our Schroth Profi II ASM FE harnesses. If the seats ever come out again, we are going to weld the mounting bolts that go down into the frame to the sliders. As it sits, it is horrible pain to install them, and we don't even have the undertray on.




Finally, we also installed our turbo blanket and some DEI heat shield on the AWIC to reflect heat from the turbo (see gold tape) and help keep things cool:



This week, our plan is to install the undertray (holes already drilled just need to rivet on), re-burp the AWIC (I had an oops today and accidentally drilled a hole through the firewall and straight into a hose), and wire in a fan on a switch for the AWIC radiator so that we can have it on before the radiator fans are triggered. Also, the center console if we have time.

[Mechie3]

Moving those tabs probably meant you didnt need to cut down the harness bar. Nice work.

[Tamra]

Moving those tabs probably meant you didnt need to cut down the harness bar. Nice work.

Yeah we noticed it didn't fit lol. Now it is in the middle of its adjustment range. More importantly though, our harness is now correctly positioned.

[tebriel]

Did you figure out if your BOV was leaking at idle? I've been trying to find one for a while that doesn't leak at idle, le sigh.

[xxguitarist]

We did not look into it any further, nor have we gotten around to plumbing it in. Our tuner just went to speed-density tuning.

[tebriel]

Excellent!

[Tamra]

Thank you!

Glad we could be of assistance ;p

[Hindsight]

Quick question: How are you filling your AWIC setup and are you running straight water or a coolant mix?

[Tamra]

We are using a coolant mix. We filled it from the AWIC first until the coolant reached the top of the hose, then filled it from the radiator with the pump running (we wired our pump to run whenever the key is in the on position). We kept moving the AWIC around to help get bubbles through it and squeezed the hoses. You can hear the bubbles going through the pump, so you can tell when they're mostly out. After the dyno session we topped it off again but it didn't take much more. We will probably check it again before autox on Sunday to see if we can fill it any further, especially since I had my oops with the drill through a hose... we already burped it once since.

Ours is closed loop. I believe if you do run an ice box, it would probably be much easier to burp, but that means you must run water - no coolant.

[Hindsight]

Thanks for the reply! So is the radiator cap higher than the intercooler? Seems like it would have to be in order for the method you posted above to work.... but I can't imagine it would normally be higher with the car resting on the ground so are you jacking up the front until the radiator fill cap is higher than the bleeder on the intercooler?

[Tamra]

We did jack up the front - sorry I forgot to mention that. However, the AWIC pump does a pretty good job of pumping it through too.

[Hindsight]

Nice ok I fully understand. Sorry - one last question: Do you have an overflow connected to the barb near the radiator cap, or did you just plug that?

[Tamra]

Tomorrow is our first autcross. It snowed lightly today and tomorrow is predicted to be sunny. It will be 22 degrees at 8am, climbing to a pleasant 39 by mid afternoon... This should be fun... if it happens. They haven't cancelled it yet. It's also only 5 miles from our house so if we end up miserable we can easily go home.

On another note, we picked up a tire mounting and balancing machine today (Our van purchase has paid for itself already). We figure the ROI is 1-1.5 years with the autox tires and some personal car swaps. Our Hoosiers are due in next week along with our race wheels! Just street tires for tomorrow.


I swear it's not an Atlas rocket...



And, while picking up the tire mounter and balancer, I found this gem that happened to be directly in route... went by, fell in love, and took her home. I sold my Mazda 3 about a week or so ago and had been keeping an eye out for an S2000, RX-8, G35, etc. This one is beautiful. All the bolts even have their original plating (we can all appreciate that after tearing apart our rust bucket Subarus), and the rest of the car is just as clean. I think the most salt the car has seen in its life was on the U-Haul trailer during the tow home.

You can never have too many RWD two seaters!

Nice ok I fully understand. Sorry - one last question: Do you have an overflow connected to the barb near the radiator cap, or did you just plug that?

No overflow with the AWIC. Per my understanding, the water temp really shouldn't get warm enough to need an overflow.. if it does we're in trouble. I'll fact check my answer with Andrew in a bit.

[metros]

Nice pick up on the s2k. Those OEM hardtops are worth a mint too!

<----Wishes he never sold his turbo s2000. *Sigh*

[Hindsight]

Wow, new roadster and a tire mount and balance setup?! Sounds like the beginnings of a very fun year! Congrats on finding the S2k. Were you sick of the FWD of the Mazda?

[Tamra]

Wow, new roadster and a tire mount and balance setup?! Sounds like the beginnings of a very fun year! Congrats on finding the S2k. Were you sick of the FWD of the Mazda?

I like to switch cars every year or so... I'm 25 and this is now my 14th vehicle (counting the 818, so you could argue 13), 3 of which have been Miatas. I think I managed to sell all of them but two for at least what I paid for them, or even made a gain.

The S2000 is very pretty though... it might last longer. We'll have to see. Most of the fun cars I wanted were RWD so I was originally planning on just throwing snow tires on for the winter (my commute is all major highways), but now I might have to pick up a winter beater. The car is so clean I would feel bad driving it in salt.


As of now, the autocross event is still on for tomorrow. We'll have to see how conditions look in the morning. Could be more like ice racing than autox with this weather.

[Mechie3]

I have a friend with a tire machine and balancer. He does tire swaps/mounts/etc for the Subaru club in exchange for 6/12 packs. He just doesn't touch cars. You either bring him loose wheels or you remove and install wheels so he doesn't have any liability for torquing them. You could recoup costs that way too (either in beer or charge a nominal fee to locals).