Gary C2 UK

Hi all,

sorry for basic Q's but I'm not to familiar with the tuning of turbo's.

I've got a boost enhancer on my car which is OK. I was going to get it chipped soon but reading about these dual port wastegates has given me a question. If the wastegate opens later allowing quicker boost pressure and higher pressure depending on setting and spring shim's etc then is this not just doing the same as rechipping a reqular engine/turbo/wastegate car?? Or would you change the w/gate AND rechip as well. I don't want to go to far with the engine just a little "pick me up"!!

In in the UK and there aren't many options for tuning these cars here.

Thanks,


Gary

IanM

If you just want a little "pick me up", then I assume you're not interested in a boost controller. If that's the case, I wouldn't bother with a dual-port wastegate. Just keep your boost enhancer. Get a set of Autothority Stage 2 chips. You won't need the banjo bolt restriction jet if you're running a boost enhancer though. I'd set the boost to a max 15psi (2bar on your gauge), and you're off. Nice and simple, with about 250hp at the wheels. Some others might argue that 15psi is pushing things, but we'll leave that up to you. My car was running almost 16psi of boost for years with APE chips and an MAF system, no problem.

Gary C2 UK

Ian thanks for the reply.

Well what I should have said was something to move to from the Boost Enhancer. Are my principles of the DPW in 1st post correct?

If I did fit the DPW I would also have the Controller. I suppose what I meant was that on a otherwise standard engine is the DPW effectively doing the same(ie same reults) as rechipping the car with a standard wastegate??

IanM

No.

Having a dual-port wastegate and boost controller will allow you to control boost. By the way, your stock wastegate would also work, but you'd want an electronic boost controller. Believe me, I've tried it. Adjusting boost with a manual controller and stock wastegate is a very sensitive affair. You don't really want to start increasing boost all by itself, with no other mods.

What a set of chips will do is allow your car to safely handle extra boost. The fuel maps and ignition curves are revamped, which keeps your air:fuel ratio and timing advance where it should be. The chips themselves don't give you more boost. That's why Autothority gives you a a banjo bolt with a restrictor jet inside it, to send less flow to your cycling valve, thus fooling your computer into allowing more boost. Similarly, Weltmeister sells their chips with shims for your wastegate, which effectively increase the spring rate of your wastegate spring, thus requiring a greater boost signal to open the wastegate.

So, either way you really need chips. At that point, it's up to you how you want to generate boost. Either leave it up to the chip manufactures, and use their shims or jets, or give yourself the ability to control boost with either a manual or electronic boost controller and corresponding wastegate upgrade.

Danno

Yeah, I wouldn't even consider replacing the stock wastegate until after I've hit the 350rwhp+ target. For now just shim the stock one and that's enough (30-minutes). In a stock car with stock turbo, an aftermarket wastegate won't give you any performance gains. Better off getting chips 1st, then an electronic boost-controller then an upgraded turbo and/or MAR kit, perhaps then a wastegate.

Gary C2 UK

Thanks Ian & Danno.

Danno you answered the question I was going to post after Ian's 2nd reply.

The best way forward then is to simply re-chip yeh? What exactly do you do to re-shim the stock wastegate. And how much difference fron standard will this make.
Even I was to simply re-chip should I still keep the boost enhancer too? Does a re-chip only get rid of much turbo lag? With the BE and shimmed w/gate will that reduce lag much?

Thanks again,

Gary

Danno

Yeah, you want to get chips first. But you have to remember that the power-increase does not come from the chips. It comes from the increase flow that you get from increasing the boost. That's why all chip kits include way to turn up the boost, like a restrictive banjo-bolt, or shims for the wastegate.

The chips just ensure that you have more fuel to keep up with the higher boost. In fact, if you install aftermarket chips without increasing the boost, you'll have a slower, less-powerful car. That's because you'll end up with a richer fuel-mixture and more ignition retard; not good for stock boost levels.

A good combination would be a shimmed wastegate with the Lindsey boost-enchancer. The shimmed wastegate increases the spring-tension and ensures that the wastegate can deal with high exhuast pressures. It would also give you more boost than the 10psi factory setting of the LBE. You may still need to adjust the LBE to get the 14-15psi of boost that most aftermarket chips are programmed for. This is an effective combo because the LBE removes the stock CV/KLR from the loop since those roll on boost too slowly and bleeds it off too early in the high RPMs.

As for lag, there's not much you can do about it. It's a side-effect of low-compression and turbos. More boost and larger turbos just makes the lag worse. Check out Farzaan's dyno charts here:Farzaan's Dyno Day and in particular, check outAPE v2.7 vs. Stock on '89 944T, shown here:



As you can see, the APE v2.7 kit reduces lag just a tiny little bit from 2000-3000rpm (light-blue torque cruve vs. pink stock one). And it gives you a higher torque peak as well. BUT, notice that the modified car has a torque curve that drops off quicker than the stock car.

And comparing differently-sized turbos can be seen here:'87 944T vs. '89 944T (both with APE chips)



As you can see, the smaller K26/6 turbo in the non-S car builds boost much quicker in the low-RPMS compared to the larger K26/8 in the TurboS car. However, the larger turbo has more lag. And both turbos have a torque curve that rapidly drops off compared to stock; a sign of a turbo that's maxed-out in capacity.

The only way you're going to reduce turbo-lag significantly is to get higher-compression pistons and put in a smaller turbo running less boost. That way, the percentage of power that's contributed will be a smaller amount than it is now in the stock car.

BTW, shimming the wastegate is an easy 30-minute procedure (provided all the exhaust bolts aren't rusted and seized):

Gary C2 UK

Danno,

thank you very much for taking the time to explain all this. I understand it a lot more now.

It's unfortunate to see the modded cars all suffer the drop off in power/torque so early. I definitely won't be stretching to a new bigger turbo. Apart from the cost there will be more lag earlier on I expect so that's not to good. The idea of a smaller turbo and H/C pistons is simple, and a lot of cars like Audi's do this. Trouble is your back to the situation where was won't get the same show in the back!!

One query regarding the stock wastegate again. The fact that the cars done 91K(although it's in good health) would suggest that the already weak standard springs probably "had it" right? Shimming I expect would probably just make matters worse in a short time. Am I right with that assumption?

I think the chip's/LBE/Stock wastegate(shimmed) would be the first step. Unless you think the DPW is best installed in place of the stock item due to above assumptions.

The trouble is in the UK this stuff is expensive so I can't go to far. A re-chip is just under $900. The DPW which is just the Lindsey item sold buy a guy over here is $660 and the controller $115. Not forgetting the cost of blowing up the engine!


Thanks again,

Gary

Russ Murphy

Danno,
Please excuse my ignorance, but how does changing to those external 3.5mm washers (are they taller or shorter than the stock ones, or are there none at all stock) going to increase the preload on the wastegate spring?
I envisioned "shimming the wastegate" as adding shims inside the wastegate between the spring and the top of the upper housing.

Danno

Hmmm, I personally have not heard of anyone having a weak wastegate spring. It should be fine with 91k and shimming it would increase the preload and have it resist exhuast pressure better. I think a lot of the mis-conceptions about the "weak stock wastegate spring" comes from people who increase boost using a manual-controller. These things only responds to input boost-pressure and knows nothing of exhaust-pressure or RPM. Thus they can't learn to bleed off the signal to the wastegate at high-RPM. And they will always bleed off boost at high-RPM. For a stock car with less than 400rwhp, the stock wastegate shimmed up to 4mm should be fine.

As for getting chip-upgrades in the UK... Hmmm, how about buying them used from the US? Typically you can find the AutoThority Stg2 chips for around $125-150 used. And shipping can't be more than $20-50? As for getting them through customs and paying VAT, can't you declare them as used car-parts for repair or something like that?

Russ, take a look at this picture of the stock wastegate:



You can see that the diaphram chamber on top contains the wastegate spring. It rests on the bottom of the chamber and the top side pushes up on the wastegate valve's stem. The diaphram chamber has a seal at the top that will push down on the valve if pressure is introduced to the chamber. This pushes against the spring tension.

Then by shimming up the entire chamber, you raise the floor of this chamber, yet the top of the valve stem remains in the same location (valve can't close anymore). This adds preload to the spring, thus requiring a higher force from the diaphram to open the same amount (more air pressure).

Since there's also exhaust pressure pushing down on the valve's head, the total force against the spring is the SUM of exhaust pressure and the diaphram. By shimming the wastegate, you provide more spring force to resist exhaust pressure AND the diaphram. This is very noticable immediately after shimming the wastegate because you will have 2-4psi more boost with the same boost-controller settings.

Luke

Speaking about Dual Ports!!!

I have an LR wastegate and Man. boost cont. Can I remove the cyclic valve all together??

the Cyclic valve is the circular looking plastic peice with a couple small lines coming out and a large line going in right? Under the intake next to the idle air Stab. V??

IanM

Yes, remove it. There are three lines coming into the cycling valve. One is your boost signal from the banjo bolt connected to the intercooler pipe. That one should already be connected into your manual boost controller. Another line goes into your wastegate, this as well should already be disconnected and used with your controller. The third line sends the boost signal back into the intake system when the cycling valve is closed. Make sure you plug this line, or directly plug the connection into the intake, or you'll have a vacuum leak.

Russ Murphy

Thank you, Thank you Danno!
I now see the light (or the preload).

Has anyone used the SFR dual setting boost controller? How is it better than a MBC/bleed valve type and how will it do a better job of controlling boost spikes?

Gary C2 UK

Danno,
thanks again for your informative posts.

Regarding US chips, what is your typical fuel Octane rating? In the UK you still get 98 Octane at the pumps. I think, although I might be wrong, that US fuel is a lower rating(91??) so your chips will be tuned along those parameters.

There is a company near me which is owned by and ex BMW Motorsport and Bosch specialist. He does his chips individually to suit each car. You are present while he runs up your car on the dyno and uses his lap-top to fine tune the DME. Once he's happy with the mapping he then burns new eproms with the mapping. It takes about four hours for a 944T due to the extra chip in the boost controller. With this in mind I think the US chips may be slightly less optimised compared to this option using the UK fuel etc. I might be wrong in this train of thought however?? What do you think?

The comments regarding the wastegate spring I made were due to what I read on the Lindsey Website. I just thought that a normally weak stock spring would have been past it by my mileage. I suppose shimming will firstly get you to the original "when new" rating and then a little extra beyond that. How much stronger will the shove from a re-chipped and shim stock w/gate be compared to a stock car?? Is it really noticeable or just pleasantly brisk?!?! I know the graphs show good looking gains but does the above mod feel like it's worth the money??

Thanks again,

Gary

Danno

Gary, I'd check around for more BMW/Motronic tuners. It doesn't take 4-hours to dyno-test and fine-tune a set of chips. Shouldn't really take more than 2-3 dyno runs with an appropriate adjustment to fuel-mixtures. Once that's dialed-in for maximum power at 12.5:1 air:fuel at full-throttle, you then start advancing the ignition timing. That would take only another 1-2 dyno runs. There's no programming that is required of the KLR chip other than removing the over-boost protection. The knock-sensor ignition retard is the same. And there's no use in re-programming the CV boost curve since you're going to be getting rid of that anyway. I've even heard of people running the stock KLR chip above 15psi and they don't get any overboost-protection cut-off at all (weird).

With 98-octane gas (is that RON or Motor method?) you should be able to run 15psi of boost without any problems with a decent amount of ignition advance as well. In the US with 91-octane (R+M/2) gas, the AutoThority chips are set to use 15psi of boost (via banjo-bolt mod). But they incorporate a significant amount of ignition retard. So much so that partial-throttle/mid-RPM response simply sucks!