eriksseven

iTrader: (6)

Anyways, this will be my third rebuild on my TII.

The first rebuild, I re-used 140k mile TII housings, did minor street-porting and got all new seals and springs (except side-seals). This rebuild failed because a corner-seal stuck. The 'tip' of one of the apex/corner seal slots was fractionally bent, so the corner-seal couldn't travel freely.

The second rebuild, I reused the original TII 'end' plates, but used 60k mile modified N/A housings, 9:4:1 N/A rotors and an N/A center iron (IIRC). I street-ported everything. There are several reasons for this motor's failure, including the fact that I reused the apex seals that had been FIRST used on 140k mile old housings. I believe this caused difficulty in the apex seals wearing properly, therefore causing long-term low compression. I also reused the side-seals and corner seals without checking their specs. This motor ALWAYS had compression numbers of no greater than 90psi all around. I detonated it several weeks ago and everything was deemed 'destroyed' (except the E-shaft).

I recently purchased a 100k mile 'coolant seal failure' s4 TII motor for $200 and discovered (upon opening) that the rotor housings and rotors were in really good condition. Except, the irons all had slight scoring on them, opposite the intake ports... All of the motors I've torn down (4 now) have had this scoring, so I know it's normal wear. I CAN catch a nail in it... But I don't have money to replace them... Will these 'trace' scratches cause low compression? Or, should they be OK to last another 50k miles or so?

Anyways, I began with porting the exhaust ports. Until 'this time around' I had been doing it incorrectly... I had been extending the port down, to the shape of the RB template, but I had made it an ANGLE up to the actual port... I know now that this will not increase exhaust flow very much, but only mess with the timing of the port (self-defeating).

This time around I've went down slightly past the RB template, which I found out might not've been a GREAT idea, but upon further inspection, I only went about 1.5mm farther down, which'll probably be OK. It's pretty big, now that all of the 'angle' material (that I had left on my previous exhaust ports) has been removed.

I'm hoping to begin the intake porting today, but I want to have a set plan before porting... I REAAALLY want to do a small bridge-port on my secondary intake ports. Street-porting is too... simple.

Now, I may have been perverted, or am holding onto false hopes, but I was told by the resident 'porter' at Atkins that a half-bridge isn't THAT big a deal... It might sound foolish, but can I do a small bridgeport and use my stock ECU? I will be running the R-tek 1.7 chip, SAFC II and a Profec B EBC, as well as 8:5:1 TII rotors.

If the answer is NO (which I assume it will be) can you explain HOW exactly a half-bridge messes with the timing and fuel delivery? I was told in another thread that it takes "unique" timing to run a half-bridge correctly. What does this mean?

Also, WHERE in the powerband will I run into problems with a half-bridge, HIGH or LOW. (idle will be set for around 1100RPM's I assume).

I don't understand how cutting a small eyebrow and adding the slightly extra airflow is such a big deal...

I want to believe I can use piggy-back systems and run a half-bridge without too much difficulty...

Please, take the time to shoot me down... lol.

BTW, I'll be running the Walbro 255 fuel pump and 720cc secondary injectors.

I don't want to hear a 're-hash' of the 'common forum knowledge' that it "can't be done". I want a re-iteration of WHY it PRACTICALLY and LOGICALLY won't work.

Thanks a lot,

eViLRotor

iTrader: (2)

Well, from comparing a few Haltech H-BP timing maps and theory to SP maps, the overall advance timing is quite a bit less under boost. H-BP's seem to like more timing in vacuum cruise bands due to the extra overlap (according to BDC).

My friends HBP (stock turbo and IC) car idles at around 1200 rpm. It required quite a bit of fine tuning to get it to run smoothly in the lower rpm's. Didn't like being below 2500 rpm until we tweaked the maps. It's ok there now, but not great.

I'm just wondering if the SAFC can give you that same kind of control.

eriksseven

iTrader: (6)

Well, I won't be able to adjust the lower RPM timing via the SAFC, but (obviously) I'd be able to adjust the fuel %.

I can slightly modify the high-rpm timing via the R-tek 1.7 chip, which I believe retards timing 1 degree, for every pound of boost beyond 10psi...

Do you know how much vac. pressure the half-bridge (your friend has) pulls at the 1200 RPM idle?

eriksseven

iTrader: (6)

Anyone else have any logical experiences/opinions? (...guesses as to what will be effected?)

ultradef

Why don't you try PM'ing BDC...he has lots of experience with HBP's.

Aaron Cake

iTrader: (1)

I do not recommend any kind of bridge on the stock ECU. I have not done it myself, but I have seen it attempted. The result is a car that is always hard to start, difficult to drive down low, needs a higher idle and has hot start issues. The requirements of a bridgeport are just so radically different (as already explained above) that the stock ECU cannot deal very well.

Also, you will run into fueling issues as you increase power. Since you are talking bridges, you're obviously looking for some real power. The stock ECU is very limiting in this case.

boostedHULK

iTrader: (1)

There are piggy back systems that should allow you enough control to make it work fair enough. I'm not saying it's gonna run perfect at low rpm or anything, but more and more piggyback systems offer spark control too. check out something like the smt-6, or the megasquirt 2 (megasquirtandspark). Since you don't seem to have any problem rippin' motors apart and trying things, i say just go for it, do the HBP, spend the 200 bux on an smt-6 and see if you can make it run well enough to drive regularly.

Stanello

iTrader: (1)

I am currently running an NA 6port full bridgeport on the stock ECU and an SAFC II. I'm sure I am limited a WHOLE lot by the stock ECU, but It can be done. I've had no problems whatsoever. Idle is around 2k, but is pretty driveable in my opinion, and have put about 3,300mi on it so far. I would think that your ECU would be more capable than mine, but I could be wrong.

::: saving up for standalone:::

Edit: You might run into problems with the S5 AFM being maxed out, but the S4 seems pretty capable.

Oh, and the Stock ECU doesnt make it a complete slouch.

eriksseven

iTrader: (6)

Nice... I've got a s4 too.

Bridgeporting will wait until another time... I've reasoned myself out of it, NOT because I don't think it's possible, or wouldn't be a blast (and a headache) but simply because it would take too much gas... Most of this gas consumption, I'm sure, would be because I'd constantly be wanting to "feel the bridgeport", lol.

Next time...

Thanks for the responses, guys

eriksseven

iTrader: (6)

Oh yeah, I've decided to do a fatty, 'BDC wanna-be' street-port.

After doing HOURS of searching these past couple days, on all the forums, I've came to realize how ***** and pointless my last streetports have been.

Stanello

iTrader: (1)

My BP gets better highway mileage than the stockport engine used to. About the same around town. I kept the stock primaries with 720cc secindaries w/FD fuel pump. As long as I stay under 4k its fine.

staticguitar313

iTrader: (2)

no more high compression turbo setup?

eriksseven

iTrader: (6)

Well, I got a TII shortblock for $200, so I'm probably going to use the 8:5:1 rotors that it came with it... Not because I necessarily WANT to, but for money reasons it's the best idea.

Cause, yeah... I kinda destroyed the 9:4:1 N/A rotors when I blew my motor, lol.

Shoot, my next motor will be bridgeported and standalone...

eViLRotor

iTrader: (2)

The the vac signal to the haltech pulses quite a bit. Usually between 10-12"

gingenhagen

megasquirt is standalone, not piggyback.