Sävar Turbo Site

Ett forum för motorentusiaster
Aktuellt datum och tid: tor jun 22, 2017 7:27 pm

Alla tidsangivelser är UTC + 1 timme




Ny tråd Svara på tråd  [ 10 inlägg ] 
Författare Meddelande
InläggPostat: fre nov 25, 2016 9:53 pm 
Offline
För mycket laddtryck

Blev medlem: sön aug 27, 2006 6:17 pm
Inlägg: 284
Ort: Denmark
Hi All.

Im building 722.6 MB automat into a 245Turbo with B234. Im making 560bhp and 670Nm on pumpgas now, but this is relatively high up in RPM compared with the original stall the E55 AMG had.(where the automat comes from).

My fastest 60foot was 1.77sek with manual 530D 5speed, but the car is very difficult to launch consistently. (street tires, suspension more trackdaylike than drag, and many other compromises)

I am concerned that i kill my 60foot times as the B234 is simply not producing the needed torque on the available 722.6 converters, so i will eventually need a custom converter.

Now im launching the car with launchcontrol, and mowing ignition to -15 degrees will very rapidly generate lots of boost. I have tested -25 and that spools really fast(above 3000rpm)

Has anyone tried applying launchcontrol with a very large negative ignition angle on a converter, and gradually phasing it back as torque and rpm climbs.

Something like this. Normal ignition table, until i active the launch control.
Then, at full throttle, lets say the engine stalls at 1900rpm with the current converter.
Then move the ignition to, say, minus 25degrees. Now the RPM drops as the engine power drops, but the ignition is now so excessively late that i can build boost, and ramp ignition back up again, effectively reaching a higher stall and match it to the greenlight so i actually have boost at the start.

I actually think it wont work, and that i would need a minimum 3500rpm stallspeed not to kill the 60foot times, but what do the audience think?


Upp
 Profil  
 
InläggPostat: mån nov 28, 2016 8:39 am 
Offline
Forumsberoende

Blev medlem: fre dec 23, 2005 10:49 pm
Inlägg: 8729
Ort: Patrick Wetterskog Ludvika
As engine isn´t producing any power with very low ignition even thou you got a lot of boost tells me it´s the wrong way.
You need power to stall higher on same converter.

Try to launch you racecar now with manual gearbox and set the timing back -25degrees from normal point.
Then let engine have this retard whole 60ft, tell me then about your loss in acceleration ;)

That´s your powerloss in 'launchmode'.

_________________
///AMG
Nån som har ett gammalt lumention tändsystem liggande för en bra peng?


Upp
 Profil  
 
InläggPostat: tis nov 29, 2016 11:18 pm 
Offline
För mycket laddtryck

Blev medlem: sön aug 27, 2006 6:17 pm
Inlägg: 284
Ort: Denmark
Well, i will rather think i need more low end torque to drive stall up higher.

I cant simulate that with the manual gb, cause what you are suggesting will obviously kill power.

I know the engine will maintain boost far better than it will build boost in reasonable time, so put it this way: If i can trick it to build boost first(just 20kpa more will help dramatically i think), then apply the load gradially(by sweeping ignition back up) then i _think_ im would be able to stall higher, and faster. Simply because the engine seems to hold boost far better than it builds boost with normal timing. For instance, the car is much faster with 10 degrees advance, than with 13degrees. It builds boost far far earlier and that seems to compensate.
When i launch in second gear with 1,5bars the car hookes up quite good given the compromises needed in street car, and the rpm at clutch drop can go as low as 3500rpm without stalling on the clutch. If i tries launching at 3500rpm without launchcontrol it wont build boost, and the engine stalls.
With the autobox/stock converter i would without doubt not reach say 2200rpm with ignition set back to minus25, but i might be able to build, say 150kpa absolute, and then step up the ignition to say minus10, producing more torque, pushing stall slightly upwards as torque increases, and be able to maintain the boost at a higher level.

I dont know, im just trying to work my mind around that converter. and the stall problem i forsee coming. The mercedes converter is not the easiest thing to get in a 4000rpm stall, and those outthere is 4000rpm stall on a hemi. That would be very different torque levels than my small low compression engine.

I started reading up on converter physics to possibly modify it myself. Thats pretty longhaired stuff that will take a while to understand....Good with some challenges.

A small shot of nitrous would maybe do wonders :hey:


Upp
 Profil  
 
InläggPostat: ons nov 30, 2016 5:08 am 
Offline
Forumsberoende

Blev medlem: fre dec 23, 2005 10:49 pm
Inlägg: 8729
Ort: Patrick Wetterskog Ludvika
Power, torque.. what' s the difference?

_________________
///AMG
Nån som har ett gammalt lumention tändsystem liggande för en bra peng?


Upp
 Profil  
 
InläggPostat: sön dec 04, 2016 1:30 pm 
Offline
Forumsberoende

Blev medlem: sön maj 22, 2005 11:11 pm
Inlägg: 1436
Ort: Skelleftehamn
One idea is to first make high boost by lowering ignition (like you said) and when desired boost is achieved you set the ignition fast to MBT (not slow) and let the converter stall with the "new" high torque.

_________________
Turboladdare är för folk som inte kan bygga motorer /Keith Duckworth


Upp
 Profil  
 
InläggPostat: mån dec 05, 2016 9:16 pm 
Offline
Forumsberoende

Blev medlem: fre dec 23, 2005 10:49 pm
Inlägg: 8729
Ort: Patrick Wetterskog Ludvika
So,, how do you get it to boost with big turbos at sub ~1500rpm AND make power?
You need power to rev through stallspeed, HUGE power, and if you succeed the converter will blow up sonner or later, probably sooner.
And you need transbrake, rear brakes can´t keep the wheels locked.
One idea is to stage in 5th gear, rear brakes receives less torque in that way.
And then slam it into 1st with electronic controller.
Butt still, It´s HARD to stall higher then converters 'tuned' stallspeed.

Easiest thing is to raise stallspeed and get transbrake, (lock 1st and reverse)

_________________
///AMG
Nån som har ett gammalt lumention tändsystem liggande för en bra peng?


Upp
 Profil  
 
InläggPostat: ons dec 07, 2016 6:31 pm 
Offline
För mycket laddtryck

Blev medlem: sön aug 27, 2006 6:17 pm
Inlägg: 284
Ort: Denmark
Well, eventually, i will reverseengineer the stock MB converter and see if i can figure out how to make it stall whereever i want it.

Actually, this is somewhat interesting:
MB used the 722.6 transmission in the c180 series with just ~129hp/5300rpm.

It would be my guess that that converter would have a significantly higher stall on my b234turbo than the amg V8 converter. They are quite a bit different internally, judging from the fin bosses you can see imprinted on the housing of the converter. Sadly, they only have one lock clutch, but hey, why should it not be possible to change that too.... :wink:

So maybe a 129hp converter, on a AMG 722 box, behind a B234T would be an attractive choice, or atleast interesting project.

I will build the transbrake on the outputshaft with an external disc brake. The MB box does not have the option of adding transbrake due to the hydraulically sequenced valves. It is not a possibility to skip over a gear on that box, nor activate "an extra gear" without serious valve housing modifications.


Upp
 Profil  
 
InläggPostat: ons dec 07, 2016 8:28 pm 
Offline
Forumsberoende

Blev medlem: fre dec 23, 2005 10:49 pm
Inlägg: 8729
Ort: Patrick Wetterskog Ludvika
Aftermarket boxes that can control 722.6 can add transbrake from what i have read.
But the one i know can do it costs over 7k skr.

_________________
///AMG
Nån som har ett gammalt lumention tändsystem liggande för en bra peng?


Upp
 Profil  
 
InläggPostat: ons dec 07, 2016 11:06 pm 
Offline
För mycket laddtryck

Blev medlem: sön aug 27, 2006 6:17 pm
Inlägg: 284
Ort: Denmark
Okay, thats new information to me. Any link to one that will add transbrake?

The box is different from say aw341 in the control method, since the electric shiftvalves are operted in sequence, not in patterns.

Regardless how you activate the shiftvalves, they only work in sequence due to the hydraulic block is hydraulically sequenced.
Hence i cant see any way i can add transbrake with the controller, since in first gear, it will only shift up to 2nd. And you cant activate 5th, and drop to anything but 4th, then to 3th and then to 2nd.

In contrast to the AW, and the electric american boxes, that can have transbrake by the controller.


Upp
 Profil  
 
InläggPostat: tor dec 08, 2016 2:18 pm 
Offline
Forumsberoende

Blev medlem: fre dec 23, 2005 10:49 pm
Inlägg: 8729
Ort: Patrick Wetterskog Ludvika
I´ll see if i can find the link again.

http://mbworld.org/forums/w211-amg/5938 ... 2-6-a.html

Yes and no,, but there are possibilites.
adding one more solenoid and modify valvepackage.
You can use if i remember correct the PCS unit to control the extra solenoid.

_________________
///AMG
Nån som har ett gammalt lumention tändsystem liggande för en bra peng?


Upp
 Profil  
 
Visa inlägg nyare än:  Sortera efter  
Ny tråd Svara på tråd  [ 10 inlägg ] 

Alla tidsangivelser är UTC + 1 timme


Vilka är online

Användare som besöker denna kategori: Inga registrerade användare och 3 gäster


Du kan inte skapa nya trådar i denna kategori
Du kan inte svara på trådar i denna kategori
Du kan inte redigera dina inlägg i denna kategori
Du kan inte ta bort dina inlägg i denna kategori

Sök efter:
Hoppa till:  
POWERED_BY
Swedish translation by Peetra & phpBB Sweden © 2006-2010