View Full Version : Map sensor info

26-03-13, 17:37
What is the rating for the std Q4 map sensor, is it a 2.5 bar sensor?

If I fit a 1.7 bar programmed chip, do I need a 3 bar map sensor to make this work? I assume there are only a 2.5 bar and 3 bar map sensors available.

If the sensor only read to 1.5 bar(2.5 bar absolute) how can the ECU adjust timing and fuel above 1.5 bar boost.

The higher range is important to me. We had before that an engine's piggyback chip was adjusted on the dyno to 7000 rpm. In real life the Alfas std limiter allowed 7200 rpm and probably a little more on overrun. On a trackday the engine was ruined as above 7000 rpm the chip was not programmed at all and gave no fuel and made the timing too fast. The engine was running to lean every time it reached the redline. Since then I make sure that there are figures in programes at levels above my parameters.

This is even worse for boost levels. If something go wrong, and they sometimes do. If the boost goes higher than planned, the program must give the maximum amount fuel the injector can give, and pull the timing back aggressively and so save the engine.

Steve Webb
27-03-13, 06:04
Hi Corrie,
the Q4 only came with the 2.5bar map sensor as standard. If you want to run at boost above 1.5bar then you are going to need to fit a 3bar map.

27-03-13, 08:18
I suspected that, I will need a 3 bar map sensor as well.

I hope to offset the bad fuel and 95 RON in SA, by taking the compression ratio on the Q4 engine down to 7.5:1 to avoid detonation. That also mean I will need to keep the flywheel std as with a lighter flywheel I may struggle in city traffic.

But that has performance effects, at 1.2 bar boost I may struggle to get the same performance as you guys in Europe with 98+ RON fuel and 8:1 CR. I will need to work on the manifolds as I intend to keep the cams standard for now.

27-03-13, 08:44
Hello Corrie....nice thread by the way. i will tell you some things
1. as Steve say if you want more than 1.5 bar boost, you have to change the map sensor so that seems, even you have the stock chip in your car you have to modify the brake points because you will confuse the ecu because in same voltage you will have different pressure.
2. are you planning to control 1.7 bar boost without external wastegate? i think you need a little of magic ;) i'm not ironic but the internal wastegate is soft and the gas will open the port even the valve don't send pressure
3. don't think that always with high boost you will have more power, all this chips at high boost has very less spark advance for being safe, so i believe that it is better for example to have 1 bar boost with 25 degrees of advance, than to have 1.5 bar boost with 5 or 6 degrees. just an overboost to high pressure gives you more torgue but 1.7 at high rpm with less advance is not the best way to remap. have you an exhaust gas temperature sensor?

27-03-13, 08:55
Your higher altitude will work against you too.

27-03-13, 08:59
are you planing for 1.7bar boost with stock intercooler?

27-03-13, 09:21
are you planing for 1.7bar boost with stock

Stock intercooler can't handle that much pressure.
The plastic ends will be your weekest point here...

27-03-13, 19:07
OK I need to explain my plans a little, first I work on ships and are currently not at home. So I am planning and sourcing parts for delivery when I am home.

I am rebuilding my engine with forged pistons, upgraded Conrods and Spesso gasket, fire rings and 12mm rolled bolts. It is all for being safe, in the TS turbos I used the standard conrods up tp 7000 rpm that is identical in every way as the standard Q4 rods. I did compare and measure them. But the Q4 piston is heavier than the TS piston with more strain on the conrod bolts and Main bearing bolts. ARP bolts on the conrods and main bearing could have done it, but it is not a std item for ARP and maybe Steve must send them samples and sell some. But I want to rev 7000 occasionally. On the TS I used the Alfa steel gasket similar to the Cosmetic with great results, up to 0.8 bar/267 whp with 1/2 " custom studs. Between brackets, I will not use a Cometic twice as the pressed dents in the gasket is now flat and it is compressed in the same way a composite gasket gets flat after use.

Radiator and Intercooler will be custom build from Aluminium and I will use a external wastegate not controlled by the ECU. (I used an internal wastegate on both TSs)

I do not plan to take the boost higher than 1.2/1.3bar, which I allready see as very high compared with the TS's 0.75/0.8bar. But shit happens, a pipe comes loose, or something goes wrong with the wastegate and boost goes higher than intended. Please don't tell me these things don't happen in Europe. And that one times cost me engine rebuilds before. But I hope this engine, with the right parts and an ECU set-up for higher boost, will be able to handle such an indiscretion. So I want the ECU to be set for high boost, but limit it to lower boost. This will not be a racer, but it will do the occasional trackday or strip event with my local Alfa club. I would love it to give stick to a new chipped GTI/ST etc.

As said before, due to bad fuel and only RON 95 in SA, I plan to lower the CR to 7.5:1 That way the timing that was programmed for 8:1 CR and RON 98 will be safe in my engine with RON 95. Naturally the Air/fuel ratio must be correct to cool down the combustion chamber and help avoid detonation together with colder spark plugs. Before I would not have used A/F ratios as rich as Mpampis, but I have learned something and if that work in the Q4 then that is what I will do, 11:1 it is.

Again I must say that every plan for the Q4 was not to get maximum power, but a reliable car with enough power to stay interesting. So the instruction to my turbo-guy was: I do not need Max power, I want a turbo that do not struggle and then give a hell-of-a-shove in the back. I need a turbo make the engine to pull like a six cylinder car, smooth. The turbo was made and is a custom Garret with a turbine AR .48 and compressor AR .7, wheel .57 Trim. This is a small turbine(matched for 2 ltr) will spin from low down and has a reasonable large outlet, not to block hot gas in the combustion chamber. And a large compressor. Now this will spark some argument, but we will have to wait 6 months or so, to see if the turbo work as planned.

It will need a exhaust that my (female) partner can live with and that help get the gas away from the turbo asap. I still debated the exhaust plans with myself, but I think it will look like this: Cone from the turbo into 76mm down pipe and where the std Q4 exhaust split in two it cone down to a 63mm and out the back with one silencer(straight through with bent pipe in silencer). BUT just before the cone to 63mm I may fit a dump valve with a 50mm port and a 50mm straight pipe out the side. The wastegate can be adjusted to open properly at 0.5 bar boost regulated from the plenum. That way the car can be driven without opening the side pipe, until low pressure is needed.

The exhaust manifold will be custom made, probably similar to existing designs. The intake will take some spit and glueing. I plan to start with the Q4 manifold, and the plenum will change into a bent box, the shape of the normal runners and still fit onto the runners with the injectors, without looking bad. It will increase the plenum to more than 2 ltrs volume, and this bring peak boost a lot quicker than with small plenums.

A single injector of 1000/1600cc/min before or after the throttle can add enough extra fuel for higher boost or 4 injectors in the plenum near the runner intake from the plenum. Fueling will be fine-tuned on a dyno with a Dastek Unichip(piggy back).

The flywheel will stay standard to help between 1000 to 2000rpm as the low compression will struggle a bit off boost. The heavier flywheel also help to get a turbo car off the mark aggressively on a strip, where a light flywheel do not and work better on track. Clutch may be sintered metal, but they don't last long and getting a Q4 gearbox off every 25000km for a clutch is a slep. But I somehow doubt if the standard clutch will do the trick??

What did I forget or what must I rethink?? Lets hear your opinions.

27-03-13, 20:32
Let me dissagree with something please. I wouldn't decrease the CR to 7.5:1 it is very low for running only 1.3 bar boost and the car at off-boost area will be extremelly slow. As for 95 RON you can decrease a bit the spark advance of the ecu. Second thing i didn't like a lot is that you are planning to make a forged engine and you will place a single injector to inject some extra fuel? Why that? How many horsepower do you want?

28-03-13, 06:43
Mpampis I agree with you. The problem is that the car will have little power off boost and with a lighter flywheel as I had on one TS it is worse. But the biggest problem is the sinthered clutch(called a button clutch in SA), to drive it smoothly you need to engage the clutch at 1000 to 1500 rpm and that is with no boost.

I would love to keep the CR at 8:1 The problem I have is first I do not have your expertise in programming the eprom, I do not have the equipment or know anybody who do. I will be able to adjust the timing with the piggyback chip, but then I can not see degrees, only a bar chart showing more or less timing advance than normal. On an Alfa you can not see or hear when knocking start on the dyno, that makes this adjustment dangerous. I used 25 deg max advance on the TSs and had no detonation, but have no idea whether 27/28 deg will be better. By going lower with the CR, I can use the setting you guys have proved to work.

I also did not liked the single additional injector and fitted 450 and 550cc injectors in my TSs before, but I could never get good fuel consumption off boost. I got 16 ltr/100km in the city traffic. The stand alone managements and the std Alfa Motronic management do not pulse the large injectors short enough to give good consumption at low load. The guys now use the std Motronic management with excellent knock control and when the boost start a single 1000cc injector add fuel managed by a stand alone management or piggyback chip for power between 200 and 300whp. I know guys with 2.5 ltr 156 and 2ltr 147s that run this system and they get 9-10ltr/100km in city traffic and 8 ltr/100km on the freeway. And these cars are reliable daily users.

29-03-13, 13:14
don't think that always with high boost you will have more power, all this chips at high boost has very less spark advance for being safe, so i believe that it is better for example to have 1 bar boost with 25 degrees of advance, than to have 1.5 bar boost with 5 or 6 degrees. just an overboost to high pressure gives you more torgue but 1.7 at high rpm with less advance is not the best way to remap. have you an exhaust gas temperature sensor?

Yes I have a Exhaust Gas Temperature sensor. What do you use as maximum exhaust temperature? I didn't have anybody to tell me what is good, I used 800C before.

I will be happy with 300whp. Mpampis, I know you plan big power with your engine, what boost will you run? What degrees Ignition timing will you use?

30-03-13, 16:00
Corrie i have the exhaust temperature sensor to the exhaust tubular manifold and i see in the track with high boost 950 C at high load. I run sometimes 1.9 bar boost but i am really scared when i use so much boost. As the advance about 33 degrees but always i use 100ron and in the tracday i use bout 112 octane. And i have 8.2 CR

31-03-13, 09:48
Halleluja. That is serious pumping air. You must post the power figures after you did a dyno run again.

I would be scared too. But importantly, nothing broke yet! So you must be doing something right.

I was too scared to use more than 25deg advance with 0.8bar and 7.5:1 compression. This was a streetcar on 95 octane.

I know guys with drag race cars and they run 7:1 CR at 2bar boost. The race class force them to use street fuel, with octane booster additive.

31-03-13, 09:48
Double post

31-03-13, 10:32
At 0.8 bar boost i have 50 degrees of advance after 5500 rpm ;) and i have 8.2 CR. i have a chiness 3076 turbo