testing waste gate pressure help/methods check
 

I just got my twin waste gates (mv-s 38mm). I took the car out for a spin, I have a vdo boost gage where the clock would normally reside, and it seemed like the boost wasn't releasing when it should. I got the set up from a well known vendor here on the site and they should be 1 bar. I suspect it is higher from the boost gauge.

I used my compressor to put 1 bar pressure to the wastegates and they do not open, they do not open at 1.2bar, but they do open at 1.4 bar. I can see the valve open as I don't have a dump pipe on them. My next step is to remove the spring and check the color.

Am I doing this correctly, testing the wastegates in this fashion? Is it reasonably accurate? I have a high quality regulator on the compressor.

As much as I would like to run 1.4bar boost I do not want to damage the motor or shorten its life substantially.

The set up is based on 993 HE's, SC cams,y pipe, and a K27HFS.

Thanks,

John

Sounds like you are doing it correctly as long as the regulator is accurate.

I opened up one of the wg's to check the spring. It was the correct spring for 1 bar for the ms-v I had. There are two different kinds depending on ship date. I then checked my boost signal hose to the wg, it was 3/16" vs. the minimum 1/4" as specified by Tial. I changed out the hose to 1/4" and added clamps just in case. Some people use zip ties but I am close to the exhaust so I used an efi hose clamp.

Did another run and it seems to be fine. My factory boost gauge shows nearly 1 bar and my CEO gauge shows 1.1-1.2 bar much better than the 1.4 bar. I did several full boost runs and I think I am fine. The volume of air must have some influence. I wouldn't think 1/16th difference in hose I'd would make a difference.

Anyone ever run a hard line for this?

Now I have to address an exhaust leak of an uneven exhaust flange mating surface on my modified 993 HE's.

Confirming you have one Blue spring in your Tial is right for one bar
Is the 993 the same car that the tial is on your testing?
Im asking because if the problem looks fixed (now) it might be because the excess pressure when tested caused that exhaust leak, and now at 1.1-1.2 because of it?

thats funny that tial says a 1/4 min. when i got my tial it came with these very small 3/16 bajo fittings. i would like to got bigger but where can i get the fittings.

thats how i tested my old WG. i put air into it until it opened. i found my valve guide was leaking.

dumb question, you putting in the right hole? pun intended.

I used the existing Banjos that were on the factory Wg not sure of diameter i didnt know there was a minimum. ill have to check the id of the aftermarket vacuum hose i put on

i know the fitting on the IC is much bigger than the one on my WG.

also, if you have a header with less back pressure i think that can raise the boost pressure.
for me, i have a .8 spring and i am getting .9 which is what i wanted.

Bench testing won't accurately verify your WG opening pressure, as you've already noticed. When installed in the car, your WG will see not only the boost pressure signal through the hose, but it also sees a certain amount of exhaust pressure. It's an additive effect and opens the WG at the required bar for the spring you have installed. Testing on the bench with just a pressurized air source will required more air pressure than expected to open it.
Years ago, I had purchased a new Tial and bench tested it for kicks....found what you discovered, contacted Tial, and they 'splained it to me.

Regardless, now that you've got the correctly sized air line leading to it, sounds like your issue is resolved.

The s I have are the 38mm x2 that were shipped prior to The earlier date as noted in the link (http://www.tialsport.com/documents/MVSspc.png). I should have a gold. Btw a padded ratcheting wood clamp works great for disassembly and assembly. The leak was caused by an uneven surface from flipping flanges. I got that fixed late last night.

Not a dumb question. I checked also. It is in the correct port for air.

Look in the right hand margin for the note in the link (http://www.tialsport.com/documents/MV-Install-Guide.jpg) I had no idea there was a min. either.


Good point. I hadn't thought of that. The 993's are a nice set up just a pain to get the nuts on 4 and 5. I also have a gt35r I just got that I may try to get in before the weekend (I have a car event).

Good point Mark. I discovered that later. I gently pushed on the valve while applying 1 bar pressure and the valve would move trying to replicate (not accurately of course) exhaust pressure.

A quick question don't mean to divert but its sort of related,

What is the actual difference in HP between 0.8 bar spring and 1.0 anyone know?

Quick question, but not a quick answer. I would say hp output would vary on several points with many combinations even to the point of environment such as humidity and temp. If it was that straight forward the dyno tuners would be in trouble. In summary, difficult to answer. Not that I can answer it, but I am guessing I am correct.

The number that most claim is around 25hp - don't know how often that has been proven on a dyno, though (and sundevil makes some good points above). Of course, if a 1 bar spring is installed, and no steps are taken to increase charge cooling (better than OEM intercooler) and monitor/increase full boost enrichment, then the gains will be almost non-existent or potentially short lived.

Robbbyg,
Are you contemplating simply changing the spring for quick hp? I wouldn't unless you take precautions of an larger I/C , increase fuel enrichment for cooling and to deter detonation, exhaust upgrades, etc. I have a 930 motor that we checked c/r before even thinking of going to 1bar. I could go as high as 1.4bar, but that would make me nervous with stock internals so I am limiting myself to 1 bar with a full bay I/C on the 930 motor with a crossed drilled crank and balanced rotating assembly as well as efi for fuel control. There is some great experience on this forum that can help.

Hi sundevil
No, my 77 930came with no intercooler, factory 0.8bar spring and factory 1.5 bar boost guage.
I have since added an OEM Intercooler from a later model 930 along with a 3.3 intake manifold, bov , msd ignition and Tial 46mm, 2 out Monty Muffler and taken off the aftermarket roof, ive kept my factory Euro headers as theyre pretty good in their own right , I havent changed the spring as yet and wont be doing it until everything on engine is Torqued and sorted . :)

I know Heat is a bane for most, but i now have the opposite problem of the engine running too cold 90 percent of the time as my engine was originally made without IC

Hi Rob, he was talking about the intake air (aka: charge air) heat which is increased when boost levels are increased (not the overall engine temperature). And it is really strange to read that you are having lowered oil temps since adding the intercooler, as an intercooler should have zero cooling effect on oil temperature. I wonder what is going on there . . .

ahhh, a 77.How nice. I am envious. I would like one of them although it wouldn't do well in Texas heat. Probably safe, but I am happy to know you are being thoughtful about it. I wish I had a clear answer for your. Ronnie is probably the clearest. It is nearly science which I never paid attention to back in the day, unfortunately. I am paying for it now. You may want to speak to Chris Carroll at TurboKraft if you haven't already. He is intelligent on the topic and has been great to deal with.

John

I disconnect the WG hose from the intercooler and connect it to my compressor and gauge.
Start the engine at idle and slowly increase the pressure until exhaust gases come out of the WG pipe (Also increase in noise) Mine opens at 0.8 bar. I used this process to adjust my manual boost control valve, i am now running just under 1 bar.
When i had my car dyno previously and adjusted to 1 bar i had an increase of 32 bhp over standard (300bhp). So approximately 0.1 bar equivalent to 16 bhp at the lower pressures on my set up.
Which at that time was all standard.

hmm was added at same time as msd, so it must be the different timing curve then:p

Good thread and diagnostics
We need a sticky on different wg/ic and turbo configubalaters that are tried and tested true that could be referred to,

Its great having books on these matters but they are generic and follow factory configs, but that wont work for many of us,, especially best uses for elastic ties lol