secondary removal how do you go......
about it . could someone who has donerthis give me the proceedure for rmoving them. and what does one have to keep connected vaccume wise ? does the prom need to be reburned ? and who does this ? also where can one get the accel injectors ? and what part numbers . thanx in advance for any help
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Pete has removed his and likes the results just fine. And, I spoke w/ Marc Haibeck about it and as it happens he has a chip profile to accomodate the modification, and is experimenting with a new table which (to me) appears to actually boost the low-mid torque a smidgen as well as adding about 5 ponies to the top end. So, I wonder if the mod adversely affects emmissions?? If not, then it really seems to be a "no brainer" to pull them and install Marc's chip. P. |
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You will need to keep the electric secondary solonoid,vacuum pump and
differantial MAP(under ECM early) (under plenum later). You will need to run from the Differantial MAP to the open port of the solonoid the vacuum pump to the closed port of the solonoid. Make sure you yank everything else shafts included use Dorman freez-plug #555-108 or equal local part store. Make sure you have Full Power ON when you go for a test drive. Enjoy. This is what i can remember off the top of my head,age is catching up to my memory. If you need more info just post. Pete |
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Or you could reprogram the PROM to avoid all the secondary vacuum checks....
Pete, did you get the other info I sent the other day? Todd |
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What Todd said reprograming the chip. Yes,got it Todd thanks. Pete |
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who can reprogram the prom to do what todd said ?one last question do you have to remove the head to pull the secondary butterflies and shafts out . pete on my cam settings 1141/2 and 1121/2. have a rear end problem on the black car so havent had a chance to dyno. will be a while now with moving in to the new house and shop.
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Todd |
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Thanks. That helps. So the ECM thinks the Scndys are closed and not expecting any indicator. But if you do the latter, how does it know to use the Open PT VE and SA tables? :-D |
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BAck to one of your original questions - accel Injectors??
I got mine from - Atlantic Speed 1/803/548-6990 ask for Scott. Ask if he gives a discount for ZR1 memebrs or Corvette Forum members - He will then give you a discount - I paid $498 for 16 of them. Part # acc150121 D.Y. 91-#267 :thumbsup: |
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That's a good price. Pete |
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wow, thanx for the info, thats why i love it here ,a bunch of guys sharing and caring enough to help:thumbsup:
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While we're on the topic of secondary PT removal, Lgaff and myself discussed the idea of just removing the throttle plates and leaving the rest of the linkage in. ECM still thinks secondaries are in. Everything works except no throttle blades in the way. And since we haven't determined yet how to bypass a MALF for SCDY PT, this seemed like a reasonable way to go. Any comments?
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Any comments on simply removing the butterflies and leaving everything else intact? |
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Scott |
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Open port throttles does not mean power enrichment is active. Todd |
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Max,
So you've left the PT settings alone and duplicated the VE and SA tables? I was thinking of taking the butterflies off the shafts but leaving the shafts in. Any comments on how detrimental that would be to maximizing performance? |
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Dom,
What benefit are you trying to achieve by removing the butterflies? At part throttle, and perhaps full throttle below 3500 rpm, there will be a torque loss. At least up to the 500hp/350 level. I experimented thoroughly a couple of years ago, by datalogging, and clearly saw higher MAP values at cruise with the PTs Open. This is indicative of a loss of torque output. Others have proven that on a big inch, or even heavily modded out 350, that a full throttle dyno run doesn't necessarily show a torque loss w/ no PTs in place. While I believe that, I have wondered at what RPM the dyno runs started. My observations are that the cross-over point is near 3000-3500 RPM. I suspect that larger displacements will lower than cross-over point. On all but the most extreme calibrations I do, I have set the Port throttle opening point slightly later than the factory setting. There is a noticeable gain in Part Throttle torque, and have not had anyone complain. Todd |
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I really appreciate that perspective. As you've noted, there are several members that recommend removing the secondaries. Marc Haibeck indicated his experience on this issue is the same as yours. No measurable difference. Clearly, if you've noted higher MAP readings at PT with secondaries removed, having secondaries "in" must help in PT response. I was looking for a way of retaining the secondary mechanism while "gaining" flow and avoiding the MALF issue. Based on what you've described, I'll leave them alone at this point. The plans for my motor don't call for anything very radical. A very streetable 12sec. car is my goal. We'll see how it goes once I put on my ported top end in the next few weeks. |
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I am no expert, and I would agree a person would expect torque loss w/removal of the secondaries.....that said, the snakerskinner program removed and siamesed the runners, and ended up with more torque, making launching at anything over 1800rpm impossible. The car had exhaust mods, and advanced cams, but was a stock 350.
Anyone know who was involved in that program? The only name I have is Scott Leon who was the GM rep who oversaw testing. Would be interesting to know what they did and why, with secondaries. LGAFF 92 ZR1 #234 |
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Scott |
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Scott,
You are free to differ if you want. I have the source code. What model year, and I will review the code again tonight to be sure. |
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This is a re post from 5/06 on that other site...the reason I still have my secondaries...and I hate extra complicated equipment as well, so I own a ZR1:icon_scra I did do coil overs with an FX3 delete though...so I got that going for me.
When I read lingenfelters book on modifying small block chevy's, he talked a lot about intake velocity. At the lower RPMs, smaller passages=more intake velocity thus making more power and torque and at the higher RPM's you want more volumetric area as the motor is pulling all the air it can and intake velocity for cylinder filling is not as much an issue. I thought that was the idea behind how our stock throttle bodies' work as well. Have ya'll looked at how small that little primary butterfly is? It's tiny...I think we need to keep our eye on the ball here. Let me quote John. "Intake runner length is one of the critical decisions in engine building since it contributes significantly to the shape of the power curve" "Condensing this very complex subject down to it's basic concepts, increasing runner length tends to improve torque at the lower RPM levels while simultaneously lowering the peak torque RPM point" Now I realize that he is speaking about a different motor, but there is knowledge to be gained here. "The other half of the intake manifold design process, cross-sectional area of the port, also plays an important role. Generally a smaller runner area increases intake charge velocity, speeding up the inlet charge, which improves cylinder filling at lower RPM levels. Conversely, huge intake manifold port runners contribute to slowing the intake gas speed at lower RPM levels, hurting power below peak torque while contributing to improved cylinder filling at RPM levels closer to peak horsepower." One more thing which I feel is a jewel should be mentioned here. On a section titled "manifold destinies" (Love it, Every ZR1 owner should albeit bittersweet) "As you can see, there are several intake tuning factors that remain constant...Intake runner size is perhaps the most important. Small runners generate great low speed torque but tend to limit top end power. Runners that are too large will be lazy at street engine speeds and contribute to exhaust dilution/reversion in the intake. Short length runners tend to emphasize top-end power while longer runners tend to increase mid-range torque at some sacrifice of top-end RPM power potential. This is about as concise as you can get yet there are plenty of questions still to be answered. The future of induction tuning will address all of these factors plus a dozen more." NOW THIS IS TH IMPORTANT PART. PAY ATTENTION "How about a variable-length, variable-diameter intake that could be long and small for good low-end power and short and fat for top end power? If that sounds too much like Buck Rogers, it's already happenend in Formula 1. Perhaps some enterprising Hot Rodder will someday build as practical and affordable and intake for the small block Chevy! Think about it." The bastards should have designed it better so it doesn't break all the time. Eyes on the ball. Rick |
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I have to agree with Todd. PT Open doesn't automatically mean the ECM is in PE mode. Several other parameters that define PE. Rick, What's the image you posted? |
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Those images were just smilies from the other forum...I just cut and pasted.
Sorry. It wasn't anything exciting. Rick :happy1: |
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I would just like to thank all of you guys for this disscussion.....I'm learning, and that's great.
Rick, thank you for reminding me to remember stuff I kind of "got" back in the early 70's.....on my LT-1 motor. This is just an observation from the peanut gallery...it seems to me that Mr. Lingenfelter was sort of describing the intake system on a LT5???:o :cheers: Tom |
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Scott |
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Do you have a copy of that datalog you could send me? Which diagnostic software?
I've looked again through the entire 90 source code (& others). No link whatsoever that I can find between the PT Open bit and the BLM cell. I have never, ever seen BL cell 18 in any of my logs. It is only a 16-byte table. Todd |
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I'm using TTS Datamaster to log. I've got one I could email too you if your interested.
Scott |
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All,
I have found the relevant section of code. It does not exist in all calibrations, and I had overlooked it before. Will write more later. Learned something new today.... :) Todd |
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Max, Good catch! :worship: |
Re: secondary removal how do you go......
Well, at least I have figured out that this routine is only present on 4 calibrations, and AYBK is one. That happens to be the cal which MaxLean is using.
These calibrations use a 20-byte BLM table (0-15, 16, 17, 18, 19), whereas all the other LT5 use 16-bytes (0-15). I remembered now that BMCB used 20, but never could determine why. More to follow. |
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Todd,
So this is limited to 90-91 ZRs? Any idea why they would remove that? |
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Todd |
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Any speculation on the function? |
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1 Attachment(s)
update -- I've finally had a chance to look at this. Several things going on...
cell 16 is the idle cell, used if tps < 1.8% and rpm < 1800. cell 17-19 are used when the 2ndary fuel injectors are on. The cells are divided by the normal RPM boundaries. I'll post the code, although the formatting is not perfect. So I'll attach a txt file for easier reading. Attachment 253 Todd Code:
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Scott |
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Scott |
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it makes good sense, actually. The fuel tables are different for PT open v. PT closed, so therefore it is logical that you would want the ability to apply a different long-term correction value to each case. One might say that would not be needed, since you'd likely be in Power enrichment under PT open conditions anyway. Not necessarily. Imagine the situation where you make a quick passing maneuver on the freeway, then quickly back off but not less than 4.7% TPS. The PTs would remain open until the TPS lower threshold is met, yet you'd easily be out of Power enrichment. What I just can't grasp is why the seemingly random application of this enhanced BLM code. Why is it not, for example, in BFXB (one of the last service calibrations released)? For the most part, the later released cals are very similar in all other regards. For me, I generally ran my 91 350/500hp in Open Loop. As long as you get the fuel tables very close to ideal, and run with consistent gas and ambient conditions, its not a problem. Its all a matter of preference, really. However, I did have it going on full-time closed loop dual Wideband O2 control for awhile, just to see if I could do it. :) Todd |
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