Except that a manual controller cannot vary VS RPM, just peak boost pressure.

So its not going to give you the same response as an electric unit.

shawnm565

Except that a manual controller cannot vary VS RPM, just peak boost pressure.

So its not going to give you the same response as an electric unit.


Well, I found you can get really good response out of a manual boost controller with some work.

With a checkball and bleed manual boost controller you can vary the bleed orifice size by slowly drilling it larger with wire gauge drill bits until the boost spike with boost onset is just gone.

This assumes the bleed orifice was non-existent or undersized to start with. You might have to buy a spare inlet nipple/fitting to start with no bleed hole on the outlet nipple.

With the check ball and bleed MBC the boost pressure has to unseat the ball and then overcome the pressure loss from the bleed orifice on the backside of the ball before it starts moving the wastegate diaphram.

If you go too far on the bleed orifice size you will again have an area of higher boost before you settle into nominal boost. Its not as spikey as the spike from not enough bleed and varies more with how you pedal into full boost.

You might actually like this as it gives good tip in torque feel, but it also takes away some pedal sensitivity as you will get more boost the slower you are on coming into the pedal.

Varying this MBC bleed size is the same as an electronic boost controller "gain" that controls the transition from staying open at low boost and then varying its duty cycle as you near peak boost.

You can get "fancy" and put a variable orifice on the MBC bleed, but I like the simplicity and bullet proof-ness of the fixed orifice and -AN lines with swivel fittings.

I did this with my Hallman Pro RX on my old 60-1 and got really flat boost.

Except that a manual controller cannot vary VS RPM, just peak boost pressure.

This is still true.
With a MBC you cannot choose to taper boost off in the higher RPM for instance if you find the higher exhaust manifold pressure from peak boost is killing power after peak torque.

Unless you did some clockwork/steam punk mechanical system that would surely be more complex than a simple EBC.

But this is a high boost/pushing the limits of the compressor kind of problem.

I fully intend to resolve the electronic boost control issue one way or another, but right now I need a car I can enjoy driving and take to the track.

Early testing says it could probably use more tuning as well on the lower end of the boost curve... I can see the needle wiggling, so that's an indicator that the A/F isn't ideal.

A quick fix so you can get to enjoying the car would be to get an extra intercooler pipe and have a Pop off pressure relief valve put in it that will release any positive pressure over 12 psi (or whatever pressure you set it to) that is in the manifold tract.
A quick replacement of one of the pipes or an additional Greddy elbow you plumb for the Pop off valve and switch out for track days and you are not going to ever show the motor more than the set pressure for the valve. Its also great insurance for your motor if the diaphragm in an external wastegate were to melt due to track EGT's or cold ambient temps end up causing extra boost pressures the value will ensure the pressure is bled off before the motor sees it.

They are used in CART so the racecars can't run more boost than the rules allow. They immediately bleed off any extra pressure to atmosphere that the turbo makes. I have been considering installing one just for safety but it could easily remedy your boost creep issue without screwing around with the actuator and exhaust restrictions.

I have an internal gate, so not too worried about failure, and I no longer have an overboost problem (without the electronic control on), so I'm in decent shape. Just need to get the spool up, and be able to raise the peak to 15 psi on the street, and little less on track.

If all else fails, Fritz has a Blitz SBIC standalone electronic controller. I'm likely to head down there this weekend, so maybe we'll try that out. The once IRP is back in business, I'll get the tuning touched up.

Ok sounds good. I will just leave this here for future reference for those wanting an easy solution to controlling boost and creating a safety pressure relief valve if something were to cause a boost creep, spike or other high boost condition. Here is a ready made solution for future reference that would do the job.

Anyone building a car that has a ton of money into the engine build might want to consider this even if your boost is under control for the time being.
928 Motorsports - Mega Boost Limiter Valve

Yeah, back in 2001 when I did my TII build I used the Greddy version of the "Pop-off valve".

It works.

Greddy one sounds like a cow fart when it opens and on my set-up it was enough to give me hesitation which is fine because it keeps you from wanging up against the overboost/venting and overspeeding your turbo and killing it and the crazy high intake temps as well.

Back in the 80's and 90's we would wire the actuator door open on turbo Z's, SVO mustangs, Turbo T-birds etc. would get crazy fast boost response and it cost us next to nothing...we used the pop off valves to keep from blowing the motors. Just adjusted them up until we maxed out the fuel.
Well, except we ran the piss out of everything and it cost us next to nothing to do it lol.
We probably ran the shaft speed of those turbos to death but we made a lot of power for back then on stock turbo cars.

The application I am advocating here isn't the above. It's just the same concept of controlling manifold pressure when there is a problem or as a safety net in case of a problem controlling boost. The pressure will bleed off instead of blowing it up.

Like stated you will be able to hear it if it does actuate at some point and it will be an incredible relief to hear a cow sound vs a blown seal.

Hey all,
So, I had a closer look at my old turbine housing... and it's pretty easy actually to see the likely issue. The exhaust left an orange deposit or buildup on the inner walls of the housing. Sort of like "flo-viz" on F1 cars, you can see where the exhaust was going.

First, look into the housing from the bottom, and you can see the inlet to the wastegate passage on what would be the front rotor is much more shallow, with less exposure to the exhaust. That passage also has a longer more tortured path to the outlet, whereas you can actually see the door through the rear wastegate passage.

Then, have a look at the underside of the wategate door, and you can see a nice, half moon shape of built up exhaust deposit from the rear rotor's wastegate passage, where as it's clean from the front rotor.

This indicates that there's significantly more flow hitting the backside of that door from the rear rotor while it's closed... and stands to reason it would evacuate more exhaust once opened.

What cutting off the T4 divider and the wastegate divider did was give the front rotor an easier flow path to the wastegate outlet... with some cost in spool from an undivided housing. We may very well have overdone the removal of the T4 divider completely, and really just needed to give the front rotor a better flow path.

So, UPDATE:

I bolted the wastegate shut to test the spool (and eliminate variables), and bottom line is 15psi at about 3400-3500 depending on the run. AFRs are mid 10's in the 2000-3500 area

I got a Blitz DSBC standalone boost controller and started setting it up. It's really nice, and has a boost source feedback input which I think helps. At +20% boost, and 100% gain, I've got a nice 12psi setting. At +35% and 100% gain, I've got a nice 14-15 psi setting. Boost is ROCK solid—maybe a little spike on the higher setting, but I could reduce the gain. 10psi by 3000rpm. The transient response is pretty nice... sure the spool isn't amazing if you're starting at 2-2500 in 4th, but you don't really do that in real life. If you downshift to 3rd, 15psi is almost instantaneous. The ideal would be if the boost limit wasn't set as a percentage, but as an actual psi target, but somehow it seems to do a great job producing a steady curve despite the variation between spring crack pressure, and creep pressure at redline.

I've declared it good enough to track it, and am signed up for a local day at Summit Point, just to test & tune.

For the future, I think I'm going to have my original housing ported—but to a lesser degree than the one in the car now. I think removing the whole T4 divider hurt the spool, perhaps with diminishing return in boost control... I think opening the path from the front rotor is the ball game. Once Ihor has his dyno up and running, I'll probably go back for some fine/drivability tuning

That's great news that you finally getting the boost level u wanted. Also why u thinking getting a retune? I thought it made decent power from speedone? Also r u running a midpipe? If so does the car smell upon startup? I am debating if i should get one but i hate rotary fumes it makes u cry, i had my days with older rotary with no cat's.

Yup, it's tuned for WOT on the wastegate spring, but I think it could use some area under the curve work now that it has boost control, and drivability tuning. I do have a midpipe, so yeah, it's a little stinky. Part of the fun.

Khris, you need a RennaTune.

My FD smells a bit but nothing horrible. I also leaned my idle AFRs out to low 13s and the car seems to like it, and about 80% of the wheel went away too :nod:

Peter emailed me an update and the boost creep is completely fixed on his car. Its holding 11-12psi at the track, even WOT through 4th gear.

Yup... boost is solid through 5th hear, 140mph+.

Boost response at normal rpm range (3k and above), is nearly instantaneous as you can see if you go HD mode on the video. At the boost you see in the video, it out drags the new GT350 Mustang with the flat-crank motor.

In the fall, or over the winter, my plan is to perhaps swap in a less-aggressively ported turbine housing and see what that does/doesn't do, but for now, it's TRACK TIME. Another run with Fritz at Summit Point coming late in the month, and then Watkins Glen labor day weekend.

Car/setup is looking good Peter!

Badass!! Any guestimates on what power level you're sitting at?

Well i'll just throw my experience into this thread. We dynoed my 91 TII yesterday in nearly 100 deg heat and high humidity. Temps held pretty well. E85 did it's job and the car never experienced any detonation. The setup and tuning was quite solid and certainly impressive. The ignition worked very well as the dyno graph was nice and smooth.

-8374 EFR IWG with turbosource cast manifold
-3" downpipe and straight through presilencer with y-pipe into 2.25" dual mufflers. (Racing beat RevTII exhaust)
-Mild street port by pineapple racing
-S5 TII internals (9.0:1 rotors)
-Stock ignition
-3" air to water intercooler

Down side is the car was boost creeping/spiking upwards of 17.5 psi. Ended up cracking the rear plate. Also ran out of fuel pump. I bought the setup intending to run 10-12 psi and no more. I also want to track my car and don't want the tire/wheel/brake budget nor the high speeds and risk that 500 hp necessitates. (Not to mention short engine life.)

My suspicion is that the primary culprit is the air-to-water intercooler, because has such a low pressure drop compared to an air-to-air intercooler.

Since the engine is coming out to get a new rear plate and may get studded and/or doweled we of course have the opportunity to port the wastegate. I like the setup but wish i had known about this prior. The car was almost built when this thread surfaced.

RockLobster,

Do you know what your IATs were with that little 2.5" intercooler? That intercooler looks like the Frozen Boost Type 20 which is only rated at 350hp (piston). You're trying to cool about twice the air it's rated for. I had mediocre luck with a Type 4 which has over twice the core volume as the Type 20. I would see 30-40F temp rise over a pull. I switched this year to a Type 15 which is about 4-1/2 times larger than yours and finally have decent cooling (4F temp rise over a 3rd gear pull, 15 over ambient).

With ambient temps that high in the dyno cell, I wouldn't be surprised if you IATs were crazy high.

Actually the piping is 2.5" but i recall now i got a frozen boost type 19 with 3" inlet & outlets. Rated for 600 piston HP. I was only planning to make 400.

IATs were good but got somewhat high near redline. Then again it was 100 deg in the dyno room when we were running it.

IMO the HX size makes as much of a difference as anything else. We got one of the larger ones. I think it's a type 118 with (2) 7" fans. If the HX can provide colder water inlet temps for the intercooler it should keep up. I'm not all that concerned if the IATs rise a bit near redline, running E85 is the secret sauce.

That's a pretty damn stout stock ignition to hold up to 500 rwhp.

FD plates don't crack at that level unless you're doing something pretty silly, what do you think was the cause on your S5 setup?

+1

do you have the late spec rear plate in yours? or just the normal S5 plate?

I assumed the late spec plate was just as strong as the FD rear plate.

link to what I'm talking about if you don't know:
Rotary Resurrection home of the budget rebuild.

His car does not have a late S5 rear plate, just a standard FC thin plate.

I didn't expect the car to make 500+rwhp at such low boost(17.5psi) power to be honest. Tune was on the light side too.

I have cracked 3 FC plates now and its all around that 460+rwhp range on stock dowels/tension bolts. All of the engines come apart with ZERO issues, and all of the cars on the dyno are extremely smooth( even with dyno set to zero smooth, graphs are like silk). All of the cars have had extremely different setups too, from pump with water, to pump with meth, to E85, from Carb, to EFI etc...

On a positive side I do know for a fact the cure for cracking plates on sub 750rwhp cars regardless of the why. Above this power level its almost impossible to prevent with heavy detonation( irons split in 2).

What is strange to me is some cars have boost creep, and some do not. I have tuned about 10 of these that hold 12-13 psi...

no. no you don't. it's completely impossible. impossible on s4s.

I had mistakenly thought all the S5 plates were the same (and more stout than the S4 plates). Hell of a way to learn....

We ordered up a new rear plate from mazdaspeed. Hopefully i will get the good one...