B21ft Ignition/fuel control

Hi,

I've had my '82 242 turbo for almost 2 years now and want a little more power out of it.

TLDR: I have Kjet b21ft- want 250-300whp. Can Additional injectors and MSD ingnition be used on top of existing Kjet to avoid a full on megasquirt conversion?

Current modifications are:
Intercooler (from 940 I think?)
90+ ex. manifold
15g turbo
740t in tank fuel pump
3" DP/exhaust w/ hi flow cat and magnaflow muffler
stock intake
MBC: 10psi

Its my understanding that there is nothing wrong with Kjet, but it won't supply enough fuel to avoid detonation at higher boost levels.

I want to avoid megasquirt as this is my daily and would like to minimize down time. I was thinking- could you not control ignition through MSD 6-BTM, and fuel through a supplemental fuel injector controller?

My build would look something like this (engine only, I know m46 will crap out much over 250bhp):
LC-1 (or equivalent) wide band
IPD Turbo Cam
Holset HY35 (15-20 psi)
B230ft intake manifold w/ 4 additional injectors
Additional Injector Controller (HKS, Split second)
secondary fuel tank and pump (similar to water/meth setup)
Msd 6-btm with boost proportionate timing retard.

I know some people might say if you're going through the trouble of setting up fuel and spark control you might as well convert to megasquirt but I think this way would keep complexity down and possibly cost depending on how things are set up.

I've been searching a lot for supplemental fuel on top of the existing kjet system and it seems some people have had the same idea as me but I didn't find any conclusive results.

Am I crazy? Should I just bite the bullet and go megasquirt? The only reason it appealed to me was being able to keep stock Kjet reliability, and only have to tune fuel for on boost performance. And since I can tune the AFRs with the injector controller/wideband I could even run race gas/e85 to boost octane even more- while I can fill up the regular tank at a gas station and not worry about getting stranded somewhere.

Not trying to get flamed, not trying to be lazy- I just thought why try to reinvent the wheel with all the fuel/timing maps when I am only trying to modify a portion of them for on boost performance. I know the set up might not be IDEAL but is it a viable option?

I have tried searching, and to me, things like the terminal 11 trick with cold start injector wired to a hobbs switch isn't the same thing- it just dumps X amount of fuel at X amount of boost and I've heard can cause bogging/righ conditions. I also feel like AIC/MSD BTM would leave me more room to grow in the future and is a little more flexible.

Thanks,
Adrian

I guess I kinda answered my own question (http://forums.turbobricks.com/showthread.php?t=29600) and that guy didn't even bother with ignition he just recurved the stock distributor, but feel like there is much more info out there on this kinda setup. I need to learn swedish and troll their forums..

250-300hp is just numbers.
You say it's a daily, but you want a Holset.
What do you really want?

You want the kool kids badge or do you want a street fighter?...or commuter?

Sorry if I was unclear. This car will be something I drive every day, not necessarily a "daily"- I have no problem with a ****ty powerband, gutted interior, high fwy rpms, etc. My "73 240z is basically that and I drove it to work every day this summer.

With that being said- I'm not shooting for a specific hp output, but rather a 0-60 goal, which may be arbitrary but that's what I'm after. On top of engine modifications I'm looking into weight savings (mentioned above), and also things like tire sizing/diff ratio (which I don't know a whole lot about).

The 250-300whp is "just a number" but it's more a range I thought I would have to land in to reach my performance goals. If I could strip out weight, not touch the motor, swap in 4.11 gears and reach my desired acceleration goals I would do that- however im not sure that's the case. The holset I already have- and after the reading I've done I don't think the hy35 (smaller ex. housing than hx35: 9cm^2 vs ~12cm^2) will be that much of a lag monster?

If anyone is around these numbers I'd love to hear details about your setup!

Your 0-60 goal would be more helpful.

Ported B21F intake or custom sheet metal.
K grind at very least. A custom grind would be best.
Open 3" exhaust.
MS or other stand alone will save you so much agro it ain't even funny.
Strong tranny.
Some kind of locking dif.

OP build a strong engine with proper engine management and you don't need to put up with it yelling on the freeway. Big torque will shove you in the back. The right transmission won't break and will keep it civilized on the freeway.
Current programmable systems cost less than a set of K-jet injectors and band-aids to keep K-Jet from blowing it up. Do it right.

In the end you'll probably be much happier with a ms setup. You don't have to fiddle with a rigged up 30 year old mechanical injection with a mess of old nla parts and msd ignition. Microsquirt is a popular affordable option that is fairly straightforward to install and tune. plus you don't have to see that kjet monster every time you pop the hood fwiw

gashog said:

Your 0-60 goal would be more helpful.

Ported B21F intake or custom sheet metal.
K grind at very least. A custom grind would be best.
Open 3" exhaust.
MS or other stand alone will save you so much agro it ain't even funny.
Strong tranny.
Some kind of locking dif.

Click to expand...

Sorry! I was typing on my laptop and phone and thought I had copied everything over. Looking for 0-60 around 5.0 seconds (this is comparable to most new-ish sports cars and I don't think [besides m46] will put stock drivetrain components under too much stress).

I actually have a B21F intake already- only problem is that I planned on using the injector ports of an EFI intake manifold (B230ft lets say), which my B21F intake manifold does not have. Did you just have injector bungs welded on?

Would you not recommend IPD turbo cam? I was reading about Turbo vs A and I got the impression that the IPD cam was preferred depending on application, especially for manual cars? I don't mind having to downshift to get into useable power band.

Exhaust is as open as CA smog will allow (already 3" w/ hiflo cat and muffler). Is porting 90+ worth?

I have a welded diff. What ever came in 82 turbo cars- I think Dana 1030 with 3.73 gears? could be wrong though. And planning on either t-5/getrag 265 swap.

It seems that everyone impulsively says ditch Kjet- but why is this? Would converting to megasquirt really be less of a headache than only tuning 4 injectors and only during a certain PSI range? Not trying to disagree, honestly curious. Most people's reasoning being "Kjet is garbage" but there are plenty of threads that I think would prove otherwise (for my intended uses and power goals). If you actually think it will save time/headache I'd be very interested in hearing why!

JohnLane said:

OP build a strong engine with proper engine management and you don't need to put up with it yelling on the freeway. Big torque will shove you in the back. The right transmission won't break and will keep it civilized on the freeway.
Current programmable systems cost less than a set of K-jet injectors and band-aids to keep K-Jet from blowing it up. Do it right.

Click to expand...

High fwy RPM was more in reference to a different rear end gear set than engine set up, like above, planning on trans swap over the summer as well. And would an MS setup actually cost less than an AIC (additional injector controller) like HKS or haltech?

I'm not sure calling this a band aid is the right term, but I definitely agree that it isn't fixing the root of the problem- although I am not totally convinced it wouldn't be a viable and possibly cheaper/less time extensive option? What about using Megasquirt only as an AIC and then converting fully later when I have higher goals/more time.

A G80 + decent rubber + 12psi and you'll be close to a 5 second 0-60.

Edit: GLT autos had 4.10
KJet sucks because it sucks! You're in CA though

I would go aftermarket ems right away. It will give you so much more driveability, it wont feel like a laggy and crappy 2.1litre with no guts off boost.

I've got a b21et with the following "specs":

stock bottom end
stock 398 head with a V cam
63lb injectors mounted in the k-jet holes in the head
intake from a b23e
90+manifold
hy35
large chinabay intercooler
4.10 rear with truetrac and m90 trans

After I fitted it with vems the driveability totally changed. Its every bit as strong as a stock b230ft for normal driving, but twice the fun when the turbo spools fully. Driving up hills i see 4psi below 1900rpm, but ofcourse its not instant boost like a mitsu or small t3. So in the lower gears the engine kinda runs away from the boost. But in higher gears (3rd and up) I see 30psi by 4400rpm.

The sweet thing about the b21et (and ft perhaps?) is the low compression, allowing for high boost and much ignition advance.

If you want a good 0-60, a much smaller turbo will suit you well on a 7.5 b21ft.
People are saying ditch kjet because:

Piggybacks have very limited applications in 2015, when a microsquirt is ~300 bucks.

Dealing with a 30+ year old efi system isnt that much fun, especially if you have an entire secondary system sitting there.

Running a bunch of extra fuel lines and injectors is hokey.

Its 2015.

After solving a little fuel issue (turned out to be in tank pump) I'm back on track and thinking about this aspect of the project.

I eamiled DIYautotune to just bounce ideas off them:

the plan would be to run microsquirt controlling (up to) 4 injectors. VE tables would read 0 up until a certain boost level (read from external map sensor) and after that point I could customize the fuel table to keep the AFRs nice throughout the whole Boost vs Rpm range.

Ignition would be a modified stock distributor, and possibly have microsquirt control that later.. so the coil signal/MAP signal would be the only inputs MS would need for now.

Starting to think about the logistics of this and have a few questions:

Fuel Supply-
Would an auxiliary tank/pump (similar to w/m injection) be a sufficient fuel source? I thought about fueling the injectors through excess fuel in the return lines of the CIS injectors, but wasn't sure if that would put too much strain on the system. Basically- how should I get the extra fuel? The idea of a 2nd tank/pump seems nice cuz then I could run e85 if I wanted to (but not get stranded somewhere without it) which would have added power/cooling benefits.

Injector choice-
I'm not sure how much extra fuel I would need but I'm thinking that since this is on top of Kjet output, that relatively small injectors (2-300cc) would be sufficient? Any ideas though?

That's it for now; I'm sure I'll have a lot of questions soon..

aprophet13 said:

After solving a little fuel issue (turned out to be in tank pump) I'm back on track and thinking about this aspect of the project.

I eamiled DIYautotune to just bounce ideas off them:

the plan would be to run microsquirt controlling (up to) 4 injectors. VE tables would read 0 up until a certain boost level (read from external map sensor) and after that point I could customize the fuel table to keep the AFRs nice throughout the whole Boost vs Rpm range.

Ignition would be a modified stock distributor, and possibly have microsquirt control that later.. so the coil signal/MAP signal would be the only inputs MS would need for now.

Starting to think about the logistics of this and have a few questions:

Fuel Supply-
Would an auxiliary tank/pump (similar to w/m injection) be a sufficient fuel source? I thought about fueling the injectors through excess fuel in the return lines of the CIS injectors, but wasn't sure if that would put too much strain on the system. Basically- how should I get the extra fuel? The idea of a 2nd tank/pump seems nice cuz then I could run e85 if I wanted to (but not get stranded somewhere without it) which would have added power/cooling benefits.

Injector choice-
I'm not sure how much extra fuel I would need but I'm thinking that since this is on top of Kjet output, that relatively small injectors (2-300cc) would be sufficient? Any ideas though?

That's it for now; I'm sure I'll have a lot of questions soon..

Click to expand...

This is double the work of letting MS run the whole show.
Just rip it off like a bandaid.

I didn't see this listed already. A great write-up on MS conversion is "From K-Jet to Megasquirt...a basic installation guide." at:
http://forums.turbobricks.com/showthread.php?t=250181

K-jet was a great system for stock setups, both n/a and boosted. It is fairly decent at keeping a steady a/f ratio, and the Lambda Sond system is even better. Mercedes, VW and a few other marques used this same system with excellent results. However, after 30+ years, things wear out. The injectors don't spray as finely, the fuel distribution head wears, and deposits build up. As cars are modded, the system can't keep up.
The main limitations seem to be simply how much fuel can flow through those tiny injector feed lines, and how much air can move through the vane sensor. Once you start modding, you need more air and more fuel. Under decent boost, you need about 12lbs of air for every pound of fuel to keep the mix cool enough to avoid preignition. Cruise you're more around 14-15lbs of air per pound of fuel. Either way, all that air and fuel has to flow through the vane and distributor head.
Once you're flowing enough air to max out that vane, that's it. The electronic injector can add some more, but only so much. It's designed to balance the trims, not make up for crazy boost levels.
Adding another electronic system on top of that is not an answer. It's the exact same amount of work to install a full electronic system in place of the K-jet, with less tuning headaches afterwards. Seems to be an easy choice.