Air/Fuel Ratio & HKS AFR Type D or L or Super HKS AFR
 

Hey Guys,

I'm running my supra now with a 3 inch exhaust, cold intake, front mount, boost controller and fuel cut defender. I plan on running 17psi on stock twins and was curious if there would be an issue with my air/fuel ratio? So, should I buy one of HKS devices that regulate the air/fuel ratio? Or am I safe to turn up the boost when I want to go fast :outahere:

What ratio should the mixture usually be at, if I decide to go with the regulators and of course I will have to buy and install a wideband with a gauge :bigthumb:

Thanks!

That's a mighty strange set of upgrades. Why didn't you install a downpipe, per 'bpu' specifications? Which fuel cut defender are you using - a GReddy BCC I hope. What about adjustable cam gears, per bpu+++ specs? For bpu, an aftermarket exhaust is unnecessary (unless that upgrade was just for looks). Oh, and that cold air intake was a waste of money unless it cut through the 'shelf' for the oem airbox. Note: The oem intake box is already cold-air, so drop in a K&N filter and you're done.

What kind of fuel do you plan to run with 17psi of boost? That's too high, even for 93 octane pump gas.

Your oem maf, ecu, and O2 sensors will ensure your a/f is correct. Your problem with being "safe" is insufficient octane, not a/f.

what would you recommend running for boost? What octane for 17 or 18 psi? I am pretty sure I am running 17 psi or around 18 psi on stock twins, I have the intercooler, exhaust , fuel cut, boost controller and so on, pretty much all the bpu's

What octane is the fuel you're using? In Cali, premium is 91 octane, caculated using the formula: ((R+M)/2). Most of the rest of the country has access to 93 octane premium, which is good for about 15psi...maybe as high as 16psi. Hitting 18psi repeatedly on 93 octane pump gas will slowly erode at your pistons, and reduce your 2jz-gte's compression test numbers over time. Your engine doesn't die immediately because your oem ecu detects knock after it has happened and then retards your timing quite fast. That's what's so deceptive about the process, leading you to you think things are okay when really they're not. If you've been running 18psi for months or years, you're probably due for a compression test to determine the current 'baseline' condition of your engine. For reference, a brand-new 2jz-gte tests at about 170psi. If you're at 155psi or lower in any of your cylinders, you either have 200,000+ hard miles on your engine, or you've been running more boost than your fuel's octane can handle.

My guess is that you'd need to add at least three gallons of VP100 to every 17 gallon tank of fuel to make 18psi safe (14 gallons of 93, with 3 gallons of VP100). To be sure, watch the voltage on your 2jz-gte's oem knock sensors. Ideally, data-log them against boost - first using straight 93, and then using various blends of 93 and VP100 to determine the ideal mix for the boost level you want to run.

Note: Off-the-shelf octane boosters don't work. When they say "raise your octane by one point", they mean 93->93.1 ...NOT 93->94.

Another option is a good methanol injection system. It's a bit more complex to install (vs. simply dumping some race fuel in your tank), it's but much more convenient in the long run.

I know it quite strange but the car came with the intercooler and aftermarket exhaust so slowly i'll build up to more upgrades. I'm sort of a newbie so bare with me... Downpipe is ordered, i just have not received it yet...I'm using a gizzmo MS-2, I bought it as a boost controller & turbo timer but it also came with a fuel cut defender built in so I thought I would just use that...I have not considered adjustable cam gears because I don't have much knowledge on it but I'm learning so ill get to that hopefully soon.

Octane wise I can only get 93 Octane so as per your recommendation I should keep it a 15 psi....so for the moment I should not have to worry about my A/F ratio if I run 15 psi correct? The MS-2 specs are on the link below if you want to check it out..

http://www.gizzmoelectronics.com/Product_MS-2.html

Thanks!

I'm pretty sure the "gizzmo MS-2"s FCD will not work properly with the 2jz-gte. Here's why you need a GReddy BCC:
http://www.mkiv.com/techarticles/bcc...GReddy_BCC.htm

Adjustable cam gears are quite easy to install, and there are well-known settings that produce a good result:
http://www.mkiv.com/techarticles/cam...all/index.html

As long as you're using the oem maf, the oem ecu, and the oem O2 sensors, you don't need to worry about your a/f ratio...regardless of the boost level. However (again) sufficient octane to match your boost level is extremely critical.

That website's description of the MS-2's FCD functionality references a "(note 1)" that I could not find. Based on that one problem alone, I'm already somewhat suspicious of this device. Again, odds are that its FCD functionality will NOT work properly for the Mkiv Supra Turbo.

Okay, understood, I shall invest in the GReddy instead, it definitely makes more sense to. To be on the safe side as well lol.
Thanks for the link, looks like there's always a way, I will get some for sure, it doesn't seem too difficult.
Seeing how I'm only able to access 93 octane I shall definitely keep my boost at 15psi.
Haha yeah, I tried to look for it as well and no luck. I checked the online manual and there is nothing I can get from it maybe you would have better luck and perhaps this could be useful for someone else making the same mistake I have lol

http://gizzmousa.com/file-copies/MS_2_Manual.pdf

Thanks for the help, learnt quite a bit today!

I think you'd be surprised. Most dyno shops, race tracks, and motorcycle shops have race fuel. Many areas have a distribution center not too far away for at least one race fuel supplier: VP Racing Fuels, Sunoco, etc. You can even run methanol injection with Isopropyl or Denatured Ethanol, both readily available from home improvement stores. Heck, worst case you could run your meth injection system with pure distilled water. Consider the alternatives, and don't limit yourself to 15psi - what a waste, considering your shortblock and head is built to handle about double that. ;)

As much as I hate to admit it, it appears I may have been wrong about the FCD function in the MS-2. According to the manual, it may work just like the GReddy BCC...better in fact, since you can adjust the max voltage level interactively on a display, instead of calibrating it with a screwdriver. Just set the max voltage per the GReddy BCC install instructions, and it may work perfectly. Again, this assumes the documentation in that manual is accurate, and the only thing it does is limit max voltage. The critical difference between devices that do not limit cut properly and the ones that do (for the Mkiv Supra Turbo) is as follows: the ones that do not modify the voltage below the cut point (usually linearly). I'd recommend you test this - use a bicycle pump to change the pressure the TPS is seeing to just below the cut point, and be sure the MS-2 isn't modifying the voltage (compare the sensor output voltage against the MS-2 output voltage) - if they're the same, it works properly...but if they're not the same, the MS-2 is modifying the voltage below the cut point and you'll need to get a GReddy BCC.

Haha yeah, I'll see if i can't get my hands on some isopropyl or denatured ethanol. Race fuel, I'm not too sure on that since I live in Africa literally in the middle of no where lol....but I see if I can find some for sure.

Okay so I did the bicycle pump test you mentioned...the results were what I hoped for...the MS-2 was not modifying the voltage, the sensor output was equal to that of the MS-2 and so I guess its working properly:bouncy:...so perhaps this MS-2 is worth the money then!:)

Thanks for the help!

Cool. Also, toluene (also known as xylene) is a good octane booster - please do some reading before using it though, I believe you have to mix in some marvel mystery oil or 2-stroke synthetic motorcycle oil along with it.

Anytime. I assume you also checked above the cut point, and confirmed that the voltage is actually getting clamped. If so, I agree it looks very good for this device.