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A way around tuning?

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A way around tuning?

Postby gse_turbo » Sun Jun 17, 2012 6:40 pm

Just as a disclaimer, I'm not a tuner, I pay other people for that. However, I want to see if there is a way around traditional tuning. I have a customer. Hold that is going beyond the original budget plans and I want to be able to offer every option that's reasonable.

So my hope is to have a detailed discussion on ways to trick the standard Forenza ecu into not freaking ou with boost.

I understand the there will be serious limitations. However, if the car is drivable and somewhat enjoyable then a tune can be addressed at a later time.

So what are your thoughts and experiences?
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Re: A way around tuning?

Postby benzino » Mon Jun 18, 2012 5:51 am

Isn't different map sensor and scaled injectors the usual way? I seem to remember that Egyptian guy talking about it a lot
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Re: A way around tuning?

Postby gse_turbo » Mon Jun 18, 2012 5:58 am

Well a 2 or 3 bar MAP and slightly bigger injectors is part of it. Certain FPR's and crank signal mods are a few additional. But I want to basically get all options on the table come up with a list of everything along with how-to's. I'd be interested in doing them and testing the suggestions once everything is discussed.
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Re: A way around tuning?

Postby PrecisionBoost » Tue Jun 19, 2012 1:41 am

You need additional fuel and the ability to retard ignition (or avoid detonation) while fooling the factory ECU.

1 ) Fooling ECU

a) change out MAP sensor
--- can make the car undriveable if you do not have the ability to tune
--- usually requires an electronic system such as a SAFC ( adjusts the MAP sensor +/- 50% )
--- can also use a MAP scaling device, converts MAP voltage at various points

b) use a check valve system to block boost hitting ECU
--- ideally the type of check valve with a spring loaded ball ( grainger valve or missing link )

c) clamp MAP sensor voltage so ECU does not "see" boost equivilent voltage
--- MAP is sensitive, the sensor bends under vaccum / boost, boosting a factory 1BAR can break the sensor


2) Extra fuel

a) add another injector
--- would need a driver circuit and a mounting system

b) add rising rate fuel pressure regulator
--- simplest way to control fuel, allows larger injector scaling
--- drop base fuel pressure to allow decent idle
--- adjust rising rate to add fuel as boost comes on
--- often very course fuel adjustment, ideally you want MAP scaling to help smooth out bumps

c) add a secondary fuel injection system
--- can inject pure methanol with a standard water/meth injection system
--- caution must be used in case methanol runs out, some aftermarket ignition systems will allow for a "low water/meth" signal to be interfaced ( usually adds a soft rev limiter with significant ignition retard )

3 ) Ignition retard
--- Full out MSD systems are the easiest, they have lots of adjustability, used ones can be found cheap sometimes
--- there are also some "cheap" sytstems that will give a generic retard of the ignition by a specific quantity of milliseconds but they can be hard to install with certain types of ignition systems


I guess the big question is how much boost, there are quite a few guys that have managed quite a bit of boost using a combination of Rising rate fuel pressure regulator and a missing link map sensor check valve

Realisticly you need some sort of wideband initially to set up the rising rate fuel pressure regulator, some companies will install an O2 bung, hook up the company wideband and after a road tune they take the wideband out and plug the O2 sensor bung with an appropriate stainless plug


Hmmmm.......... I was just thinking..... the forenza is a returnless system isn't it???

That screws the idea of a rising rate fuel pressure regulator.

There are "adjustable" secondary fuel pumps which can be put in line to increase the fuel pressure but they are usually very expensive.

For small changes you can get a variable voltage system for the fuel pump, it will drop the voltage down to 11V in order to decrease fuel pressure and it can boost up to 16V to increase fuel pressure.
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Re: A way around tuning?

Postby ls400x » Sat Aug 18, 2012 11:59 am

Why not just see what the threshold of detonation is by testing and limit boost to just under that until the customer can afford a non-ghetto solution?

I am sceptical that a check valve arangement inline with the MAP sensor signal line would be successful but am happy to be proven wrong. Are they known to physically fail when subject to > atmostheric pressure?
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Re: A way around tuning?

Postby PrecisionBoost » Sun Aug 19, 2012 5:01 am

ls400x wrote:Why not just see what the threshold of detonation is by testing and limit boost to just under that until the customer can afford a non-ghetto solution?

I am sceptical that a check valve arangement inline with the MAP sensor signal line would be successful but am happy to be proven wrong. Are they known to physically fail when subject to > atmostheric pressure?


The issue here is that the ECU will go into limp mode if it sees a voltage level indicating the MAP is seeing something more than standard atmospheric pressure ( 14.7psi )

Even if you clamp the voltage so that the ECU does not see a voltage correlated to above atmospheric, the ECU will not add fuel, quickly lean out and blow the engine.

So your suggest to add boost until it detonates seems a bit off center and as far as the check valve, there are tens of thousands of cars out there using mechanical ball style check valves.

You must be thinking of the plastic check valves they use in brake boosters, they are shit and will often break with the additional pressure of boost.

The type I'm referring to is a steel ball with a spring, many are suitable for use up into the 200psi range so they will not fail when subjected to any type of boost seen in automotive.

As far as being Ghetto fixes, a significant number of people use these simple tricks to boost naturally aspirated engines.

Obviously as someone that has worked in a tuning shop, you want to always push the more expensive standalone or piggyback electronics solution, but you still need to protect the factory MAP if your going piggyback.

For example, you might add a Greddy E-Manage piggyback and use a standard Greddy MAP sensor for you piggyback.

You still need the factory MAP in this particular case, as you still need to feed that raw data into the factory ECU.

The Greddy E-Manage will allow you to clamp the voltage to the ECU, but the factory MAP will be damaged if you are running significant levels of boost ( sometimes as low as 4psi of boost over atmospheric will bend the factory MAP sensor element enough to break it )

If you add a mechanical check valve it will make sure that the factory MAP does not see more than 1-2 psi over atmospheric ( as an initial pulse ) and in most cases it will keep it nice and happy right around atmospheric pressure.

Some factory MAP sensor elements might take 20psi over atmospheric, some only 4psi, realistically there is no way to know because the manufacturers only design them to take the pressure for which they are designed
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Re: A way around tuning?

Postby ls400x » Fri Aug 24, 2012 12:55 pm

How does the check valve know what atmospheric pressure is and it should close the line to the MAP sensor? Just as an example, the manifold pressure on an engine with forced induction might range from 0 to 200kPa absolute, with 100kPa being atmospheric pressure. You want it open in all cases from 0kPa to 100kPa and closed from 100kPa to 200kPa. How can a simple in line check valve achieve this?
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Re: A way around tuning?

Postby benzino » Sat Aug 25, 2012 11:28 am

spring tension...
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Re: A way around tuning?

Postby ls400x » Fri Aug 31, 2012 12:13 am

I'm saying you cant achieve this function with a spring loaded check valve as it operates on a pressure difference across it's inlet and outlet. I has not atmospheric pressure reference. I'm saying the effect will be the same for each of these 2 cases: (1) 0kPa absolute manifold pressure (say idle) to 100kPa absolute manifold pressure (say atmospheric, throttle wide open) giving a difference of 100kPa. (2) 100kPa absolute to 200kPa absolute manifold pressure (atmospheric to one bar boost), giving a difference of 100kPa.

The pressure change of 100kPa is the same in both cases yet it's being said that the check valve knows the difference between both of these cases and will function differently for each. I'm happy to be proven wrong.
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Re: A way around tuning?

Postby chip18sw » Sat Sep 01, 2012 4:45 pm

So no funds for engine management? That sounds like a no starter to me. I'd look into an E mange blue at a minum, you can find them on E bay for arround $200 US and a DIY water injection kit would allow you to run factory timing, Sorry that's not what you were asking but that's whatI would tell him. Good luck.
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Re: A way around tuning?

Postby PrecisionBoost » Mon Sep 03, 2012 12:54 am

ls400x wrote: I'm happy to be proven wrong.


I understand your confusion, your confused about how you insert the check valve into the system to fool the MAP.

If you simply put one inline without atmospheric bleed, it does not work, the pressure on the ball/spring must always be relative to atmospheric pressure.

You attach the line from the manifold to one side of the check valve, then on the other side you attach two lines, one to atmosphere ( open line ) and one to the MAP sensor.

The best arrangement is a mechanical check valve ( steel ball with spring ) with the open line connected to an adjustable bleed valve

Under vacuum the ball valve opens as it pulls air from the atmospheric bleed, depending on the bleed hole size you will have two factors, dwell and line pressure

I know your first thought is that the MAP will always see atmospheric, but it doesn't, your bleed hole is small, thus it does not affect the vacuum by any significant factor.

This is also why you want an adjustable bleed valve instead of just an open line, then you can adjust the dwell and line pressure.

Sure if you had a 1" bleed hole then it would severely affect the reading, but you have to remember nearly all sensors using vacuum have a small bleed hole for atmospheric pressure ( including the MAP sensor, or it wouldn't function )

A hole as small as say 1/8" will make very little difference in true vacuum reading due to the massive sucking power of the manifold.

You can even run lines open as large as 1/4", but that does start to create differentials between the MAP line and the actual vacuum in the manifold.

I don't have the figures off the top of my head, but the MAP line vs manifold pressure might look like this for different holes:

1/32 hole -- line 100% identical to manifold pressure
1/16 hole -- line 99% of manifold pressure
1/8 hole -- line 97% of manifold pressure
3/16 hole -- line 95% of manifold pressure
1/4 hole -- line 90% of manifold pressure
1/2" hole -- line 50% of manifold pressure
1" hole -- line 10% of manifold pressure
2" hole -- line 1% of manifold pressure

Again this is just an educated guess of a guy with two engineering degrees and 22 yrs experience with cars.

The second factor is dwell.

If you have a tiny bleed line ( 1/32" ) then it will take time to suck enough air volume into the line to open the ball valve.

Alternatively with a 1" bleed line it will open the ball valve instantaneously.

So....... it's a trade off.... dwell vs actual pressure reading

That is why a bleed valve is best, you can simply adjust the bleed to a position where it has very little if any dwell, yet the pressure in the MAP line is very close to the actual manifold pressure.

If done right you can get very low dwell and nearly identical MAP pressure vs manifold pressure.


The Synapse engineering Missing Link has been designed specifically for this application, they have probably sold hundreds of thousands ( if not millions ) of these mechanical check valves since they started out.

Their valve has been specially designed to give nearly zero dwell ( milliseconds ) while giving your MAP line nearly exactly the same pressure as the manifold.

Not sure how they do it, all I know is that it works very well in this application.


I'm sure that there are tens of thousands of modified cars using spring loaded ball check valves inline with the MAP ( thus ECU ) from seeing boost and freaking out ( pulling fuel and timing )

I have used a mechanical check valve for many years with factory ECU's and never had a problem.

Hopefully that puts this to bed, please trust me that I have been doing this a very long time and I know what I'm talking about.
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Re: A way around tuning?

Postby ls400x » Mon Sep 03, 2012 1:21 am

Ah ok, the description of "check valve" didn't indicate that it was a adjustable mechanism with an atmospheric reference. Sounds much like a simple boost controller in operation, I can see how what you described could work.

2 degrees in the field of engineering? Bachelor or other?
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