JDUBB

So I've been trying everything I can possibly think of to get my knock counts tuned out. I'm using EBL and the only way to get them to go down is to lower timing between 2k-3k then no power. KC mostly occurs in that range. This is my first project and it's a 383, 454 TBI on a Performer RPM, 9.5 SCR, 7.9DCR Aluminum Etec heads. I've had no problem with WOT timing at 26 degrees at 3200+rpm. However this tip in and load KC at lower rpms I simply can't get rid of without losing power. It happens on a quick pedal depress howeveer if I press the pedal slowly I can avoid the kc. Need help here, running OL at 12.9 to 1 target WB should be plenty of fuel. I keep going back to the cam being the culprit to tight for the build, I'm hoping to get this tuned out. Has anyone had problems with too small a cam and the problems like me? The cam is a comp 260XFI 59degree IVT. This is a brand new motor 2000 miles so far. Other though is performer rpm manifold is too large not enough velocity and fuel is dropping out of suspension. I would really hate to have to give up and change the cam and fuel injection system.

Guest

Flat, or roller?
Flat: "Good low end & mid-range for TPI 350 with aftermarket chip and upgraded exhaust."
Roller: "Superb low end and mid-range for 350 tuned port injections."
If this is what you want in your 383, then try premium pump gas, AND several different brands of octane booster. One brand per tankful, run it virtually empty before switching brands.
Also, you can de-sensitize the knock sensor.

JDUBB

It's a full roller setup w/1:6 Comp Magnum Gold full roller rockers the cams 59 degree abdc IVC valves .575 lift with the 1:6 rockers. After all this tuning time it is all I can come up with as an explanation. I built it with intention of good low end and midrange. I've run premium fuel and tried regular and it really doesn't make a difference, I've even tried torco race mix a full 40 dollar gallon to a tank of fuel (turned my plugs brown!), fact is it seems it just can't take any timing below 3000 rpm, the trend seems to be under load heat builds in the combustion chamber and then detonation starts to occur. I've been easy on it the whole time don't want to ruin my $2000 rotating asembly- blow holes in the forged pistons. Money is really no object I just want to figure out what is wrong. Could the spark be too weak? Thats the only other thing I can think of. Anyway suppose the cam may be too small? Suggestions greatly appreciated from tuning to mechanical. I'll order whatever is needed and give it a try thanks. And I really don't want to desensitize the ks because it's the only thing protecting the pistons from a hole or ring land breaking.

Guest

I'm no whiz at PROMs, but I have done detonation enough times. If you get knock retard but have no audible knocking, then a bit of de-sensitized sensor testing isn't dangerous. Dangerous is when you start seeing micro-flecks of aluminum on the spark plugs.
For where you're going with this, you would need a cam that costs you torque below 3200 RPM. Something wilder than the XFI 280.
You say money is no object, so you can buy parts, and buy your way out of this mess. But on a budget, you could swap to 1.5:1 intake rockers and retard the cam 4 degrees, then do more testing. Both of those, especially together, will reduce your dynamic cranking pressure at 2000 RPM. Actual torque loss will come mostly from the rockers. What you lose in cylinder trapping from the delayed IC, you gain back with the delayed EO, giving the pressure another 4 degrees of time to act on the crank.
Others will refute this, but I claim it anyway because my own experiences with replacing stretched timing chains is that the newly-relatively-advanced timing adds no noticeable low end torque, but causes a noticeable loss of top end.

JDUBB

Thanks for the reply ronnjonn, Actually running tbi on a performer rpm intake maybe that's my problem hopefully not, got alot of time invested in this setup. I just went for a run and pulled plugs 1 3 7 5 I have some color on 1 but 3 is basically bone white with no color along with the others I checked. Funny thing is I'm running open loop at 12 to 1 right now so should be plenty of fuel wideband matched nb voltage at lambda -stoich I just recalibrated that also. Can too high a dcr cause extreme combustion temps? Plug aren't melting or anything just running way too hot and I've gone down a heat range. Almost seems like engine is lean but it's sure eating fuel 8-10MPG LOL. Has anyone had problems with performer rpm intakes being to large a plenum? Maybe I'm over thinking all this, just want to get it right so I can enjoy.

Guest

I think you're bone white because you're beyond the upper limit of what those injectors can flow at 100% duty cycle.
If anything, the plenum is too small. Try an open spacer. That'll let both injectors feed each cylinder.
As for your MPG, what's your cruise RPM?

JDUBB

Bone white is going no higher than 60 injector DC, I actually have a 1" spacer on it. Cruise at 65 tc locked is around 1800, unlocked 2200 ish I have cruise SA reduced to 29 degrees right now. Just went for a datalog drive and had 3 counts at 29 degrees 2200 rpm, and alot of other areas between 2-3k rpm. Crazy thing is when I free rev motor I get knock counts all over the place, looks like a rainbow arc in the data log when I rev it quick. If I rev it slow and gradually increase the rpm it doesn't happen. Same with acceleration- ease into it and go WOT does ok no count's- that's why I'm baffled it's got to be cam, fuel. or spark issue. Gonna go make a few adjustment and data log again be back in a while.

305sbc

iTrader: (3)

It sounds to me like you have typical fuel distribution error, as well as the typical brief lean-spike when hitting the throttle with TBI.
If it's brief and you're not hearing the knock, then it's probably nothing to worry too much about.
Fixing it completely could take a lot of monkeying around, or a swap to MPFI.

Guest

Okay, the spacer explains the DC.
You should be over 20 MPG, 383 at 1800 RPM with a small cam.

RBob

iTrader: (1)

I've been running the Performer RPM intake on a 331 SBC for a number of years now. Works well with a 2" bore TBI on top.

One thing I did is to run coolant through the exhaust crossover. The heads ('113s) don't have the exhaust ports and just block off the cross over in the intake. So drilled and tapped the choke pads for some fittings and run coolant through it.

I mention this as I wonder if you are having a fuel distribution issue. Caused by the intake being too cold.

The OEM TBI intakes are fully water jacketed.

The other thing I did was to cut down the plenum divider. Very much like the Air Gap version of this intake.

RBob.

morgsie

iTrader: (1)

How much of the divider you removed? I just got my intake and will be running it on my TBI setup with dctrumpets squarebore to tbi adapter and BB TBI

JDUBB

Thanks for the suggestions guys. I think we're on to something with the fuel distribution error. Rbob mentioned the coolant crossover through the exhaust crossover, unfortunately I don't have one with these Etec heads however I did see the pictures of it in the (Giving up on single plane thread) good idea. My performer rpm manifold is a standard vortec carb unit (non airgap) I did not cut down the divider in it as Rbob did. And as ronnjonn said should be over 20mpg I would think at least close however my 10mpg is awefull. And as 305sbc said sounds like typical fuel distribution error, How can I fix that, is there a fix? Swap manifolds, or cut down divider?

RBob

iTrader: (1)

JDUBB, the coolant is run through the intake manifold, under the plenum. This can only be done when the heads don't have the crossover. As they block off the under plenum passage. I posted pic's on the TBI board. I'll find them and post a link.

morgsie, JDUBB, the plenum divider. IIRC, cut it down 3/4 to 1 inch. Check Jegs/Summit for a picture of the Performer RPM Air Gap intake. That resembles what I did.

RBob.

RBob

iTrader: (1)

Here is the thread that shows the coolant through the crossover:

https://www.thirdgen.org/forums/tbi/...gle-plane.html

RBob.

Fast355

iTrader: (2)

That sounds like mechanical noise to me. Loose flexplate bolts or loose converter bolts, etc.

JDUBB

Can't be just put new tranny back in first new one I blew up, and I have an ATI SFI flex plate with ARP studs torqued per Drawing. One thing for sure is the pistons sure are loud till it warms up forged JP pistons once warm they make a little sound but not alot. Not pistons though if I reduce timing to 15 degrees I get rid of all kc but no power.

Guest

If it was me, rather than modding the RPM yet, I'd try a Super Victor Vortec, with no spacer, for a couple of weeks, then sell whichever manifold seemed more difficult.
This is what nitrous guys do when they have mixture distribution problems with dual-plane intakes.
Adding coolant under the TBI is for emissions and maybe cold driveability, not mixture distribution. The stock TBI manifolds suck at distribution.

Orr89RocZ

iTrader: (20)

With fresh plugs, and after going for a cruise, if there are some bone white ones and some normal tan-ish colored ones, then it looks to me its a distribution issue. Only way to compensate that is to tune for the leanest cylinder but that can mean an overly rich cylinder at another location.

You could have the manifold flowed and then ported out to even the flow. Improving the distribution there may solve some problems.

Or just go to a port injection system I never understood why people mess with TBI


Edit: And I dont think that cam is too small for that compression ratio. It may be some other issue, either too sensitive of a sensor, false noises from mechanical vibrations somewhere, or the fuel issue. To me, the plugs tell the story.

JDUBB

You know Orr89RocZ I believe your absolutely right. I went back to the basics this weekend and started reading the plugs after 4 datalog drives with various spark tables modifications along with running anything from 11.8 afr - 13.0 afr open loop pulling over on the side of the road pulling lugs and reading them. Some have a bit of color and a good smoke ring others are obviously receiving less fuel. My poor fuel economy is a result of having to run so much AE. So this is all starting to make sense I'm looking at port injection setups. I'd like to keep EBL and use the stock sensors harness and wideband I have if possible. Whats the best setup? I was looking at Motorvations MPFI, or perhaps a HSR.

Ronny

iTrader: (1)

I had fuel distribution issues with a XRam I used a while back. Actually I had 5 honey colored and 3 gray plugs when i yanked them. I would rule out false knock first. Do you have access to race fuel? I think most cities have a pump to service racers. Run tank down to minimum and add in 5 gal of race fuel. If still KCc then it is false. One could also retard at the distributor 3 deg at same time during the test.

JDUBB

Ronny, I did try running race gas I poured a 40 dollar gallon of Torco race mix in with a tank of fuel- effective octane was at least 110+ I believe the ratio chart called for a half gallon to hit 105 octane. I started off with half a gallon and still got counts so I poured the rest in and still got some although a bit less. Anyway it was so much it turned my plugs and O2 sensors brown and the engine began to run rough because it was fouling my plugs. I also removed 10% spark at a time and ended up with the same results as premium fuel anlot less kc but no power. I wonder if one of those swirl design spacers would help as this all happens when the tbi blades are cracked part throttle? Ease into full throttle and I'm able to avoid the KC.

RBob

iTrader: (1)

Have you tried the burst knock logic to get rid of the tip-in knock?

Rbob.

JDUBB

Yes I have and that did seem to help a bit. I can feel the retard for a moment on tip in and it did remove a modest amount of the kc at tip in.

Jdubb

JDUBB

So I've been reading about plugs and NGK says to drop a heat range for every full point of compression. This weekend I'm going to get plugs 2 heat ranged cooler thats a total of 3 less than recommended by Edelbrock- and see what happens maybe the plugs are too hot. I'm also going to put one of those swirl spacers on to see if that helps with fuel distribution too. I'm pretty convinced the poor fuel economy is due to the amount of AE needed to keep the manifold wet, kinda like a 4bbl carb- a press of the pedal and alot of fuel from looking at the data logs most of the excess fuel is used on AE. Since this is my first project has anyone converted from TBI to MPI if so what was the reduction in AE encountered 10% 25% even 50% just curious. Actually have my answer to the question "EDIT" looks like 70-80 percent less than a TBI unit.

Fast355

iTrader: (2)

Short answer NO, my MPFI setups like just as much AE if not more than the TBI. Almost every engine I tune runs best at the track and has the best driveability with a haze of grey smoke out the exhaust when you hammer it.

GOTCHEVY

iTrader: (1)

Fast355 I've been tryin to get some advice from you...check your PM...I've seen a video on YouTube of your tbi engine...what cam did you have on that thing? It sounded rough

JDUBB

Here's a snip of a log from last week with a bit of retard at tip in going from 30 degrees at low mph cruise. Any suggestions