Stu @ M Developments

iTrader: (12)

Over on another topic (here) I was asked to explain a comment I made about the fact fitting a japanese type boost controller to an engine mapped on an Amal valve (Any Cosworth or Rs Turbo) can destroy the engine.

Having replied in quite a detailed manner with pictures, It occured to me that it might make an interesting topic for folk who werent aware of this fact, so... here we are.

Ok,
This isnt going to be the easiest thing to translate into words, so I hope the pictures help.
(one is 2wd and ones 4wd but same engine specs. Ive graphed road speed in 3rd so only one "curve" to look at)

Lets look at a typically standard Amal valve controlled boost curve for a standard YB with Siemens 55s and T34 turbo.



Ok, so note that we have a nice big slug of midrange boost at 31psi and then the boost tails down. Now, for those of you whom have never considered why this is, its because as the turbine housing exhaust pressure increases as the engine pumps more and more air through it per second, it starts to overcome the spring pressure in the wastegate and opens it a little.

When this is allied to the fact that the turbocharger is well out of its efficiency range we have only one result - the boost starts to tail down... its an inevitable curve caused by the bleed off method. As a matter of fact worth noting, when using amal boost control, the boost spike is largely determined by the fuel we have available at 6500rpm and as such, how much boost we can have at 6500rpm. Essentially, we up the boost in the midramnge according to how much we have left of it at high revs when we are running out of injector opening time. (Induction stroke time base)

So this engine will have been checked and calibrated when mapped as follows:

• 4600rpm - 31psi - fuel ok - no detonation
• 5000rpm - 31psi - fuel ok - no detonation
• 5400rpm - 30psi - fuel ok - no detonation
• 5800rpm - 28psi - fuel ok - no detonation
• 6200rpm - 25psi - fuel ok - no detonation
• 6600rpm - 24psi - fuel ok - no detonation
• 7000rpm - 23psi - fuel ok - no detonation

That map would be perfectly safe to mail out to anyone with a YB and that engine spec controlled by an amal valve and couldnt achieve over 25psi after 6000rpm. Happy days.

However, lets get that same car back in and fit a cheap electronic boost controller with no overboost facility and see what happens to the boost curve to keep the same engine safe.



The very same engine is now running....

• 4600rpm - 25psi - fuel ok - no detonation
• 5000rpm - 25psi - fuel ok - no detonation
• 5400rpm - 25psi - fuel ok - no detonation
• 5800rpm - 25psi - fuel ok - no detonation
• 6200rpm - 25psi - fuel ok - no detonation
• 6600rpm - 25psi - fuel ok - no detonation
• 7000rpm - 25psi - fuel ok - no detonation

As you can plainly see, the boost curves generated by the 2 boost control systems are very different indeed, and since that controller cant have an overboost function, the boost is set to the max those injectors can deal with at 6500rpm, which on this particular engine turned out to be 24psi.

Now Imagine if the owner had just thought, well, it used to run 31psi, so I will set it to that. This same engine would have had 31psi from 4600 - 7000rpm as the boost doesnt tail down with a good controller because good boost controller monitor the boost pressure and opens/close the wastegate accordingly to ensure the set boost pressure is maintained.

With a jap controller set to the same boost as it used to "peak" at on the Amal system, that same engine would now run:

• 4600rpm - 31psi - fuel ok - no detonation
• 5000rpm - 31psi - fuel ok - no detonation
• 5400rpm - 31psi - fuel ok - no detonation
• 5800rpm - 31psi - fuel lean - probably no detonation
• 6200rpm - 31psi - fuel lean - probable detonation
• 6600rpm - 31psi - fuel lean - probable detonation
• 7000rpm - 31psi - fuel lean - probable detonation

Happy days, lets roll, here comes the boost!

• 5000rpm... 31psi yeah!
• 5500rpm... Feeling good still, in fact its a lot faster! What a great investment!
• 6000rpm... God, I cant believe how much faster it is now... Awesome!!
• 6500rpm... I cant believe this power, I wish id bought one years ago... (Judder) wait, what was that misfire?
• 6750rpm.... Its still pulling hard... god, i'm quite scared... (rattle, tinkle...)
• 7000rpm... BOOM.
• 6600rpm... Hazards on.... coasting to a halt.

Of course, as long as its mapped to suit, you will be fine, this topic is just to highlight the danger of just swopping controllers without understanding the implications.

jaiscossie

Very interesting, Does this include the likes of gizmo and the greddy boost controllers?

Stu @ M Developments

iTrader: (12)

Yes - Any boost controller with its own map sensor will usually try and maintain the target boost that you have asked for.

rhinopower

I've never though that using a separate boost controller is the best idea, particularly when the standard / aftermarket ecu can do boost control and mapped to suit!

Ben26

nice little read that mate , cheers


not that I could or would fit on to my fezz

delbee1

You must be reading my mind

For the last few days I've been reading in to boost controllers and air injectors

Can you not get surge using the amal valve?

I thought boost controllers were the newer way of doing things and air injectors the old way yet everyone still uses air injectors

Why do people change to electronic boost controllers or air injectors then??

jontysafe

I think it`s more of a case of getting electronic boost controllers and your fuelling set up properly rather than not using them?

It was my original thread, I have an Apexi ACVR boost controller because of the gear boost mapping function.

GVK.

Quality explanation!

SBT83

Nailed the explanation Stu!!!

studabear

Stu,

Does any of this apply to a aftermarket ecu and a boost control solenoid (looks like a electronic bleed valve)?

Or is it a case that once its mapped/tuned leave it alone?

jameswrx

Indeed. Not sure I 100% get the point of the thread really. You can get boost spikes on EBC's, something like the AVCR would be able to be setup to replicate the Amal valve pattern.

Also, what was the target boost on the Amal valve map?

Would you really expect a flat boost graph on the same turbo (as the Amal valve graph) with a target boost of 31psi on an EBC? I wouldn't have thought so if it was out of its efficiency range using Amal its not gonna be working miraes just because an EBC is trying to hold 31psi?

Karlos G

iTrader: (4)

This applies to any situation where higher than previously mapped for boost is ran, be it earlier in the RPM range or later... It was never mapped for it so probably isn't safe.

Karlos G

iTrader: (4)

Thats correct, Stu was just pointing out the danger of swapping from one method to another.
The point of the thread is to make people aware of a possible danger when going from Amal control to EBC (Spike and fall to flat boost curve).

Yes you would expect a flat boost graph, certainly when using an AVC-R as it has RPM vs Duty table's, you can eliminate the initial spike and then force it to hold to the limiter (Turbo allowing).

Rod-Tarry

Everyone not had air injectors for 10 years & more.

timster

Do electronic boost controllers only apply to a minimum level of power? i. e. As the one you've described Stu?

Rick

Piggybacking anything is always a little risky, especially on old ECU's with no thermal or knock management. The thing to do is to map the load sites which should not be reached to be very rich so power drops off as much as possible.

Rick

boost monster

Interesting stuff. I didn't realise they worked in different ways I always thought a boost controller could infinitly vary the boost to what ever it was programmed to. Every day is a school day.

jontysafe

They can. As stu says, so long as it has the fuel supply from the ecu.

Rs1

iTrader: (1)

Is it the cheap controller with no overboost protection that is the issue or the cheap ecu that is shown to have no overboost protection either,lol.

Marc sierra

iTrader: (1)

I thought that with Siemens 55s and a T34 the injectors could flow more than the turbo, so running lean at high revs would never be a risk.

Why wouldn't the wastegate be pushed open at high revs when using a boost controller? If that is the case it would be possible to go over 400 bhp on a T34 with an electronic boost controller, right?

jontysafe

Not if there is no fuelling chart on EPROM, wouldn't matter if you had 83lb injectors. As for 400 from a t34 see "boost spikes" and compressor map efficiency.

robrs2

The air pressure to the actuator is not applied, so it will just remain closed. It will only open when the pressure is above the set limit, the electronics open the solenoid to apply air pressure to the actuator and it will open.

fuzzy

as usual your threads seem very informative and helpful but as usual i still have no idea what your talking about....

Stu @ M Developments

iTrader: (12)

Don't misunderstand my topic.
I am merely trying to show that most people don't realise their boost curve is both expected and required by the programmer of the chip. Deviating from it can cause terminal damage because people don't realise that even though they run 31 psi at 4000rpk, they can not usually still run it at 8000rpm with a MUCH larger injector for he simple reason that we have only half the time to inject fuel so need an injector twice the size to get the same amount if fuel in.

Air injectors are an ecu controlled version of an electronic boost control valve. We have a map that says X boost and Y rpm = Z duty cycle, however this is nothing like as impressive as a modern jap style controller that regulates the boost to within 1 psi and will actively regulate the waste gate to maintain our target boost. Air injectors are just on a programmed duty cycle and as such are even affected by ambient air pressure, which is why the adjustable air injector boost knob was developed. (No, it wasn't developed for you to have low, medium and high boost boys...lol)

A good boost controller, setup properly by a pro will always be far better than air injectors.
Their biggest downfall by far, is that you can mess about with them. Lol

Stu @ M Developments

iTrader: (12)

There are a lot of controllers out there that don't allow a spike mate, let alone rpm dependant curves. And the fact remains, that if you were going to buy a Ł500 controller and replicate the exact boost curve of your Amal valve.... You would have just wasted a lot of bloody money. Lol

A good boost controller will overspeed the hell out of your compressor to achieve the desired boost by CLOSING THE WASTEGATE totally. That isn't possible with Amal as its a bleed off system and always has a feed to the actuator.

Stu @ M Developments

iTrader: (12)

Far from it mate, we fit them to stuff like stage 1 Rs Turbos and they work extremely well indeed.

Stu @ M Developments

iTrader: (12)

Not possible on an injector not capable of supplying the fuel at 8000rpm for a GT30 at 30 psi for example.
You can set all the opening time you like, it won't stop her melting down if your on Siemens 55s.

Stu @ M Developments

iTrader: (12)

Over boost protection wouldn't have helped. If graph 2 was set to 27psi that engine would have melted, yet the owner would surely have set his over boost setting to around 33psi, since he had a 31 psi spike on his Amal setup?

Stu @ M Developments

iTrader: (12)

Indeed it is. Yes. But the turbo becomes as consumable as the oil.

Stu @ M Developments

iTrader: (12)

Sorry mate, please explain what your not comfortable with and I will try to explain better.

Psycho Warren

iTrader: (5)

So stu, whats the modern equivilent of the amal valve and lecktron valve (for p8)??? they are getting hard to get hold of these days (especially latter) and obviously are old so liable to die.

Is there a modern "bleed off" replacement for the amal valve that the webber ECU's can run??

jameswrx

That was sort of my point regarding you saying 'turbo allowing'. I've used all the jap boost controllers.

Obviously I understand what Stu is saying to warn people. I think maybe I read it as a sort of diss towards EBC's whereas you could say there's nothing wrong with controlling your boost via EBC as long as its setup right. Some of the older Jap EBC's work quite well in a basic way with the gain for a spike

delbee1

What do you have on your car then Rod?

What I mean is you still see a lot of cossy's running air injectors as apposed to electronic boost controllers

jontysafe

The flatter curve is better for me because of traction issues, a sharp spike and I`d be all over the place.

delbee1

Explained very well, thanks the other threads I've read haven't explained things as well

I was actually looking into an eboost 2, has some great features, controllable gate pressure and gear based mapping but as I've said a lot of people are still using air injectors just wondered why this was

Jay,

iTrader: (4)

So realistically this topic should be renamed THE UPS AND DOWNS OF THE ORGANIC BOOST CONTROLLER

JamesH

iTrader: (21)

I believe Rod has an SM4 ECU, which has a built in MAP sensor and an external boost control valve, operated by the ECU

Glenn_

iTrader: (1)

Just a quick question can cossies and escort turbos run safely without an amal valve.

Interesting read about boost controllers.

Rick

Yea, I was going to say you need the injector headroom. You'll have some protection for actuator lines coming off this way too

Rick

BIL N KEL

Stu does that mean that an 'off the shelf' chip is not suitable for someone running a ebc then?