Turbo experts: Tial wastegate advice needed

logician · 09-20-2006, 04:03 PM

I'm looking to get a Tial wastegate to replace my leaky stock unit. In browsing the Imagine Auto web site, I saw a few old postings saying that the Tial wastegate springs seem to produce .1-.2 bar greater boost than their rating. Is that the consensus here for 930 turbos?

My '86 930 is completely stock, and I'm out here in CA with only 91 octane gas. Any recommendations on what combination of springs I should order for the Tial so I get good but *safe* performance? I would also like it to be safe for track days where the boost would be active much longer than just driving around the street.

Thanks in advance for the help!

-Juan

tsuter · 09-20-2006, 04:14 PM

Tial wastegate springs are color coded and incremented in .1 Bar. They are very accurate. You should run a spring rated approx .2 bar below what you want to run and use a boost controller to adjust the level up.

Here is a link for the springs.

http://www.nolimitmotorsport.com/prod/tialspring

I runa .4 bar spring in my low boost app and adjust up from there.

pjv911 · pjv911's Garage

Im not an expert with 930 performance but do have much experience with turbocharging in general. In my opinion I would buy the spring thats rated for the boost you desire. Worst case situation you may have an extra bit more power. I can`t see that the slight increase in boost wouldnt be compensated by the stock fuel system.
Again im no expert on 930 cars and figure someone soon will add another opinion.
BTW do you have a reliable boost gauge ?

Kurt Williams

WydRyd · 09-20-2006, 07:07 PM

I always thought the TiAL's were pretty accurate w/gates and you should just order the base boost spring you desire. If you have an EBC/MBC, then you can just order a lower base spring (say .8bar) and adjust up accordingly. If there's boost creep, then that may be a function of the design of the headers and the power levels you're aiming for, and you probably need to run two wastegates (one on each bank).

tsuter · 09-20-2006, 07:17 PM

One reason you run a lower Tial spring rate and an EBC/MBC is it is a PITA to change springs and the guy said that he wanted to occasionally track the car. In that case you run one rate on the street and do a couple twists on the MBC when you track. That way you're not running the higher boost during the 98% of the time on the street. Believe me you are on the boost every day when driving even if you think you can hold back.

A second reason is technical and has to do with keeping the signal away from the wastegate until the MBC/EBC releases. But this reason goes well beyond the scope of the question.

logician · 09-20-2006, 07:44 PM

Hey everyone, thanks for the replies. I'm not using a controller, and would be happy to run the same boost on street as track. So I have to rely on the Tial wastegate to limit the boost accurately. That's why I'm so concerned about the accuracy of the springs. You guys with aftermarket (accurate) boost gauges, how much does the reading deviate from the spring calibration when you turn the boost controller all the way down to give minimum boost, i.e when the spring is setting the boost not the controller?

I do have a boost gauge, an Andial connected to the brake vacuum line. Hopefully that's accurate, but I have nothing to compare it against. So what do you consider safe boost? I was going to order a .9 bar with .7+.2 springs. But now I'm concerned that might be too much when including any spring calibration error.

-Juan

tsuter · 07:51 PM

Sorry, I can't advise on what is safe in your car. I run 8psi in one and 23psi in another. Its all dependent on your setup, age, condition, gas....

edit..there is no deviation to the gauge vs the .4 bar sping nor the 1.4 bar spring at the manifold. They are very accurate. Off the brake booster I'd guess you may read 1-2psi low The cannister volume is the reason.

WydRyd · 09-20-2006, 09:04 PM

I have a NHS boost gauge which connects to the brake booster and it's pretty darn accurate. I've set my EBC to 1.05 bar and the NHS boost gauge shows eactly that.

I recommend getting perhaps a 0.8bar spring in the TiAL unit and running an EBC to vary & set the max boost you wish to run.

The advantage of running a 0.8bar spring is that you can turn off the EBC if you run into bad gas and run a safer level of boost until you can get better fuel in there.

I'd hate to run a high base boost spring and regulate boost with my foot when/if I come into bad gas and the thing pings like crazy

Be safe and set the w/gate to 0.8-1.0 bar and regulate further if you like with an EBC or MBC.

beepbeep · 09-21-2006, 01:49 AM

What they said. Buying a wastegate with hi-boost spring or changing stock 0.7 bar spring for 1.0 bar spring is unwise. Changing springs is PITA and once you run into a batch of bad gas or extremly hot weather you won't be able to do anything but stay off the throttle.

It's better to get 0.7 bar spring and just add a regulator after that (electronic or mechanical, doesnät matter).

mb911 · mb911's Garage

the springs are very accurate. However I would suggest you use a boost controler to increase as this is the easiest way to do this safely. When My engine was running properly(before the signal line came off/melted mine was dead on at 5.8 psi(.4 bar) with my guage(handheld) I have run 38mm tial and 46 tail and have a bunch laying around if you need any all new. anyhow thats the deal

hobieboy · 09-21-2006, 05:20 AM

I think the old postings you read was due to the use of after market headers that was not able to dump excess exhaust fast enough. My GHL does that.

Wrt spring, I agree with everyone that get a lower spring & use a controller to fine tune it. You can "add" boost easily but you can't go below what the spring is rated for.

slow&rusty · 09-21-2006, 06:43 AM

I have run TiAL wastegates ON MANY cars that I own currently and in the past incl. my 930 and yes their spring rates are very very accurate - no issues there.

Yasin

bkreigsr · 09-21-2006, 07:16 AM

fwiw, in answer to you question, I did notice higher boost readings on the stock gauge after installing one of IA's k-27s units and a Tial with a .8 spring.

On acceleration, at WOT, I am reading 1 bar on a regular basis.

bill k

logician · 09-21-2006, 08:13 AM

Thanks for all the replies -- very helpful. Based on all the replies, I'd like to learn more about boost controllers that I could use with the Tial wastegate (the original wastegate is wasted

and needs replacement.) I've read a bit about them, but would appreciate any information.

What units do you guys recommend? Electronic or mechanical? I've seen some posts using a boost spring as low as .5 bar with an external controller. What are the tradeoffs with the spring used with those external controllers? I like simplicity and reliability. How are these things for reliability? What are the scenarios where they could malfunction and overboost?

Bill K, where you using aftermarket headers?

-Juan

bkreigsr · 09-21-2006, 08:24 AM

Juan, yes, I installed a full B&B system, K27S and the Tial back in June. I tried to fit a euro ex system but it would not clear the clutch linkage on the shorty trans.

(system is for sale plus a modified oem muffler)

recommend if you are thinking of aftermarket exhaust, talk to Steve at IA. he has a killer ssi system that I'm sorry I did not get.

Bill K

WydRyd · 09-21-2006, 02:09 PM

There are a temendous amount of variables that determing the right w/g spring to run. Even changing your muffler would change the spring required.

If you had to run a 1.2 bar spring to reach 1.0 bar, you're seeing too much back pressure.

If there's a muffler on the w/g, it'll partially offset the effect of backpressure opening the valve and you'll have to lower the spring.

By removing the muffler off the w/g, it'll flow more with less back pressure (on the exit side of the valve), and you'll end up having to run higher spring pressure to compensate.

If your turbine's too small, it'll make so much backpressure that you'll have to run a lower spring because it'll make more boost with the same exhaust pressure.

If your w/g valve head is too large, it'll be affected by the backpressure in the exhaust to much and tend to fall off on boost on top.

If your w/g valve head is too small, it'll climb due to lack of flow.
etc.
etc.
etc.

As I said above, to be SAFE, get a 0.7 or 0.8bar spring and adjust boost levels with an EBC or MBC. They are very accurate if setup correctly

tsuter · 09-21-2006, 04:44 PM

Here is a pic of the MBC I run on the 911, It is very reliable and good for managing boost of 0-5 psi or so above the spring rate. I.e., your wastegate spring is say .8 Bar or 12psi with the MBC you manage between 12 psi and maybe 16-17 psi.
There is nothing simpler.
Now on my other turbo I run an EBC but now we are getting more complex.
Ther are many many choices but they all do the same thing.

This site has a smorgasboard of boost controllers.
http://www.slowboyracing.com/more.php?id=1020&