[riceetr]

well last night i hooked up my friends scantool and went on a top speed run in the car at 19 psi to see if it runs lean and the duty cycle of the injectors. i got on it and in 5th gear at just a hair past 150 there was a little bang and the car nosed off. i thought it was fuel cut. i replayed what happened, seems our cars do not have a fuel cut, we instead have a boost cut. but thats not bad whats bad is that when the boost cuts the engine detonates bad. so i recomend no one does to many high speed runs at 19 psi.

cliff notes......150ish at 19 psi, engine back fires and car noses off. boost cuts and engine detonates. I.E. do it too much engine go boom.

 

[Samel_Camel]

RiceEtr,

I don't want to throw you for a loop, but if anyone ever blows an engine it'll be one of us on this board. there is no "boost cut." If you are running your engine at 19psi with no fuel adjustment, you are experiencing knock. It is "knocking" at lower speeds, but you don't have any way of telling until you get it in such a bad position (such as running the engine at 150mph) that it causes SEVERE detonation. There is a fuel cut, however, your car may never see it if the engine keeps pulling spark until you cause detonation....

Seriously guys. Manual boost controllers and stuff for testing purposes with "moderation." Please don't blow your stuff up, please?

-Sam

 

[ekool]

You probably hit fuel cut, but the scan tool couldnt (or didnt) update fast enough to pick it up. Pulling fuel caused the car to run lean enough that no combustion process happened, thus causing the boost to drop (not enough exhaust gasses to keep it spooled) -- The detonation was caused by running lean.

Just my guess.

 

[riceetr]

well, frommy play back, the injectors were still at 98% suty cycle at the jut. and also, DSM's do the same thing w/the boost cut, they even make a boost cut protector, and its not like we don't have a DSM engine. im putting 2 and 2 together. saw fuel, no boost and detonation, and DSM's do the same. tried using logic here.

 

[ekool]

ricetr,

My supra also has boost cut, and we also use the boost cut defencer (I use an HKS FCD)... all it does is limit the "boost" signal the ECU sees so that it never hits boost cut.

However, when you hit "boost" cut, the car just cuts ALL fuel off... thats what makes it feel like the 'oh shit i just hit a brick wall feeling' -- Oh, my DSM also has hit boost cut on at least 5 seperate occassions

 

[boost junkie]

well, frommy play back, the injectors were still at 98% suty cycle at the jut. and also, DSM's do the same thing w/the boost cut, they even make a boost cut protector, and its not like we don't have a DSM engine. im putting 2 and 2 together. saw fuel, no boost and detonation, and DSM's do the same. tried using logic here.

Can you please explain to me what a boost cut is? If you have manual control over the wastegate, how is the ecu cutting the boost?

If you saw 98% duty cycle on the injectors and your still pushing the car to the redline in 5th gear, you are going to be the first to blow up your engine. I hope you live near me... I want the intake manifold. :lol:

oh and PS: It's definately not a DSM engine :roll:

 

[1slosrt]

well, frommy play back, the injectors were still at 98% suty cycle at the jut. and also, DSM's do the same thing w/the boost cut, they even make a boost cut protector, and its not like we don't have a DSM engine. im putting 2 and 2 together. saw fuel, no boost and detonation, and DSM's do the same. tried using logic here.

Can you please explain to me what a boost cut is? If you have manual control over the wastegate, how is the ecu cutting the boost?

If you saw 98% duty cycle on the injectors and your still pushing the car to the redline in 5th gear, you are going to be the first to blow up your engine. I hope you live near me... I want the intake manifold. :lol:

oh and PS: It's definately not a DSM engine :roll:

From my DSM tuning days, any injector duty cycle's past 90% means you probably need bigger injectors. Injectors don't operate well at 98%!

 

[Exhaust Depot]

yup, just like Ekewl said.

Fuel cut is the same thing as boost cut.

HKS makes the FCC Fuel cut defensor for my supra.

GReddy also makes one called the BCC, Boost cut defensor which is what I have.



The car sees X amount of PSI and the next thing you know is that the fuel cuts out for a split second and the car feels like you hit a brick wall. Its like driving in 5 gear then throwing it into 4th and getting off the gas.

When you have a boost controller of any kind, you just defeated the ecu's means of controlling boost.

When you hit fuel cut, you have no fuel, hence no exhaust, hence no energy to spin the blowdryers to make boost.

 

[Exhaust Depot]

OH yeah, there is also a possibility that you did not hit fuel cut but the cars speed governer?

 

[Mike B.]

I was thinking the same thing. Could have been the speed limiter or overboost protection. The ASD controls power to the fuel pump and the ignition, not boost. Like Hector said, if you have no ignition and no fuel it would be slightly difficult to make boost. :wink:

Could also have been overboost cutout, which has the exact same effect. The ECM sends a signal to the ASD which cuts out ignition and fuel.

 

[Exhaust Depot]

Mike,

Whats ASD?

 

[Mike B.]

Sorry, "Auto Shut Down" relay. The power for the ignition and the fuel pump/injectors go through this relay. The ECM controls the relay.

 

[Exhaust Depot]

Ah yes, I read about tha ASR in my maint manual. I just have not memorized all of the little alphabits yet.

 

[riceetr]

boost junkie...actually our engine is basically a DSM engine. who owns Mitsu.....DC....correct. whats our engine code? 420A whats the GS engine code...420A. same engine in essence just a little more displacement.

car companies do it all the time. Camaro's and Vettes both have Lt1's and LS1's

the probe and MX6, same engine same basic car.

 

[Exhaust Depot]

Well I dont know who does what but I can tell you what the manifold says on it.

Has a little diamond on the exhaust manifold.

 

[PB Pod]

Here is my understanding of the origin of the motor. The 2.4 16 valve DOHC in the SRT-4 was designed and is exclusively built by Chrysler. It began life as a SOHC 2.0 in 1993. The DOHC 2.4 first saw life as the Dodge/Plymouth minivan base engine in 1994. There is also a SOHC 1.8 version used exclusively in export Neons. In 2002 it was dubbed the PowerTech in the Jeep Cherokee.

It was never part of the Diamond Star project. Mistu has never manufactured the 2.4. There are some who have suggested that Chrysler copied the head design from Mitzu, but that is not the same as it being collaboration. The block and bore centers are very similar to the previous generation Chrysler 2.2 and 2.5 motors In fact, swapping the 2.4 head is being done to these motors.

I would be interested to learn of any Mitsu connection to this motor. I have no problem with Mitsu, in fact I like them. There is a red Evo VIII sitting at a lot five blocks from my house that looks SWEET!

 

[lifeisdeath]

GReddy also makes one called the BCC, Boost cut defensor which is what I have.

BCC = boost cut defensor? hmmm....shouldnt it be BCD?

 

[lifeisdeath]

OH yeah, there is also a possibility that you did not hit fuel cut but the cars speed governer?

i think it was SCC that got the car to 153. they didnt say if it was indicated or actual though.

 

[lifeisdeath]

whats our engine code? 420A whats the GS engine code...420A. same engine in essence just a little more displacement.

Engine
Engine Code : A853

http://www.sportcompactcarweb.com/roadtests/012scc_dodge/index.html

 

[Blue05SRT]

fuel cut

At least on dsm's, I had two talon awd's. what they do is fuel cut, and fuel cut on those cars is when the ECU reads to much Air and just simply what it does is cuts fuel off so that boost drops. Also want to find out more about this go to VFAQ.com they will have all ur answers there for a dsm, but hey a car is a car no matter what brand it is so they all have something in common, at least the fuel cut part.