Ill try to keep this short..
Had a consistent 13.40 car. Have Mods which should have put me in the 11's. Ran a 12.82 best (consistent 12.80s in 100 degree heat)
Directscan shows a nasty 3rd gear. Problem is my rpm's dont increase on a steady up-slope through 3rd. Actually, right after 2-3rd shift, rpm's stay at 4100 for 1 full second before climbing to 4200 where they stay for another half-second. During it's "climb", DS shows my rpm's DECREASING 50rpm at various points in the run in 3rd gear. The 3rd gear graph looks more like a gradual hill then a "slope" upwards in rpm. 1st and 2nd gear are tight, and go by fast. However, i noticed an ever-so-slight leveling off in 2nd gear at around 4100 rpm as well, but it went by really fast.
Question is:
Is this Trans? Ignition?
I have a 1-month old coil on the car. No knock or retard at all during the runs. New R42ts plugs gapped at .035, accel 150-ohm racewires, good voltage, etc.
The car doesn't feel like it's slipping at all, but my top end is suffering to climb in 3rd, and thanks to directscan i can see in .05 increments exactly where it has problems. I saw a sample-graph of a known-ok GN and it's 3rd gear looks like a ramp, not a gradual slope like mine does. That was a 12.44 run @107mph. Mine did 12.82@107 with a crap 1.97 60-foot (100 degree track :P )
Before i buy a new tranny - what else could i possibly investigate further so i dont spend $3K on a trans only to NOT fix it?
Here's what i have:
87 GN - 15,000 miles
3-inch THDP with hi-flow CAT
New o2 (readings are ok - 7.9 to 8.0)
43# Lucas 009 injectors
TE-44
Billet FPR
Adj Wastegate
27lbs boost (NO KNOCK)!!! :P:P:P
112 octane
TPS-TEC
Walbro 340 hotwired
Hooker 2.5 duals
RJC Powerplate
K&N 9" in-stock canister
Driver & Passenger breathers
New EGR
New Coilpack
Accel 150-ohm racewires
Delco R42TS@ .035
Nitto 275/50/15 drag radials
Red's 107,Red's 93, and a custom chip from BM computersource (Bob Moreale is an awesome guy, and a LOT of help!) Cant say enough good things about him.
Red's chips knock on my car - too rich for it. Not his fault though as they were setup for only the 009s and downpipe at the time.
Help! I need my top-end fixed! I just BARELY beat a Z06. His 12.85 to my 12.82....a win's a win though! By the way - shifts are HARD, and authoritative. There is NO evidence of slippage in any gear that i can tell. TCC locks-up, 60mph "keep steady throttle, hold foot on brake, and rpms should climb then decrease while holding 60mph" test passes, etc.
I need thoughts, experiences, opinions, you name it. This is a potentially VERY expensive problem for me, and i can't play guesswork this time
What could possibly cause this!?!? It's keeping me out of the 11's whatever it is!
Thanks!
Jay
87GN
Glen Ellyn, Illinois
email: GN@wideopenwest.com
I have a dumb question, are you racing with the cat. on the car? What's TPS-TEC?Is that the TPS box that fools the computer???WHY? What are the o2 readings when in third at 4100rpm? Did you try another chip? This happened to me a while back, I would put the race chip in, and third gear would lay down but wouldn,t stay there as long as yours. It would run terrible at the track, then when it was time to go home (with the street chip)it ran great. Just for s&g try the street chip for a run or so. Maybe the car doesn't want to be locked up yet. What else is BRAND NEW? Maybe the car doesn't like something you JUST did. All just suggestions. Tuning, don,t you love it!
thanks for the reply
to answer your questions/comments here goes:
1) Yes, the CAT is on the car. It's a 3" hi-flow. There is an 11.60's GN running the same downpipe cat i have, and he doesn't have the problem. I figured that would eliminate that as a possible culprit. ?
2) The TPS is the box that compensated for my TPS' inability to read past 4.18V stock. I honed the bores by the screws, did all the calibration possible..still no good. I had to get the TPS to get WOT readings. The TPS holds steady now at 4.88V throughout the entire run.
3) O2's @ 4100rpm are 8.3-8.0 with Red's 107 (there was some retard with his chip - 2.7 degrees for an instant at the end but average was about .6), and with the chip from BMcomputersource O2's were steady at 8.0 with no knock and no retard.
Red's chip was a lot worse than the BM chip which makes me question the tranny. Im still new to the TR world, but if it was tranny slipping - wouldn't it be CLIMBING rpm's, and holding steady MPH instead? In my case - the inverse is happening. Also - no matter what chip i use, my car shifts from 3rd to OD at 4800 rpm. Seems awful low.
The only recent addition was the hooker duals. I've had a problem with 3rd since i bought the car 2 months ago, but now that i have directscan and a LOT more HP - it's starting to really affect my times. BONE stock I ran a 14.00 on original 87 Eagle GT's...the car was quicker than usual even stock, but not fast enough to make me notice this problem.
Do i have too much power for my tranny? I got my hp peak and torque peak right at the shift recovery points to complicate the issue...
Thanks for any help provided.
Three thoughts. 1, are you "sure" you are not getting KR. Have you checked the knock sensor to make sure it is working? 27# of boost is a LOT. You should be running c16 or the equivalent at that level. But if you do that high flow cat will be a no flow cat in short order. Lead plugs em really good. 2. Are the origional valve springs in the car? if so even with the low miles they could be very weak and limiting your top end. 3. Consider putting a visible fuel pressure gauge on the car, taped to the windshield, and insure that you are getting static plus boost pressure for a total of (example) 43 static and 22# boost should show 65# fuel pressure wot going through the traps.
I'm betting on tired valve springs if the're origionals.
Good luck, and turn it down some till you figure things out.
Dwight Hayden
dwight,
1) Yes - i can send the directscan file if you'd like to see it. NO knock counts OR retard @ 27lbs boost with the BM chip. I got quite a bit of knock with Red's. I know - nobody can believe it either. BUT - it's a MILD street chip. The timing is set at 18 degrees vs. 24 with Red's. This was a test chip to eliminate issued with my previous detonation and 3rd gear probs. We eliminated detonation, but 3rd still sucks.
I can remove the CAT if i MUST, but really dont want to. I can hollow it out i guess, but really dont want to unless it's going to make a big difference. It's 3 weeks old. 2) Yup - original valvesprings. Car has 15K miles on it. It sat for a long time, and as such valves were open/closed for quite a while without getting any use im sure.
3) Fuel pressure is verified good via windshield-guage
I have more fuel than my car can use if i want it. FYI - I have no more adjustment on my adj. wastegate - it's as short as the rod can go! I wanted to keep turning it up till i got knock or retard, but had ZERO with the BM chip! I swear on my life! I was knocking quite a bit with Red's chip leading me to believe 24 timing is just too much for my car. 18 was too little..maybe 20-22 is perfect. It wasn't a custom chip for my car - just a test chip he had layin around for me to try.
I just checked some prices..
Valvesprings are cheap. Question is - should i just get STOCK replacements, or slightly more? WHEN i go 11's I dont want to mess with anything underneath the valvecovers. If i did - i'd be building a bigblock instead. My goal was to get 20mpg+ on the street and steal $100K "sportscars" of their dignity with a sleeper! That Z06 made me sweat too much..
Any part numbers for valvesprings that will let me go 11's with NO other engine mods whatsoever? I couldn't find any info on that on this site. Knowing me - if i take the valvecovers off and need to go further..the engine's gonna come out and i'll end-up dumping $10K in it. ;) The money's not an issue, but my time and labor is. I want to keep this simple as i've done all the work with myself and 2 friends so far.
..i got my credit card waiting...;) I can dump $30-$100 on long-lasting springs no prob if it's gonna help. Anything's better than a new tranny! I want to make sure its TOAST before I pay $$$ for a built one.
BTW - for what it's worth..I can't believe these cars run what they do for as little mods as they receive. Im an old-school V-8 kinda-guy, and just can't believe these cars can run 12's with $1000 in mods. Unbelievable machines! ..and embarrasing to all that get whooped by one. ;)
I'd bet my money on the valvesprings. Just because they have low mileage doesn't mean anything, they are still 15+years old. And like you said, sitting open/closed for a long time couldn't be good for them either. I'm gonna hazard a guess that even brand new they were marginal (ie same as the other 3.8 valve springs.) But these motors don't need to be spun high, so maybe they were ok new.
For the tranny, I'd think it would rev(ie rpms go up) if it were slipping. If you are worried just smell the fluid, if it smells burnt, or is discolored, then you may have something else to worry about. 27psi is alot, I've run about 22psi on straight 116 and ran a 12.48@110, so something doesn't seem right there. Not saying you can't read, I'm sure you can
, just wondering about your boost numbers, maybe bad gauge? But if your rod is as short as it goes, then maybe it is 27, just be careful, one hiccup and Kablooey! One more thing to think about, the heat will kill our cars, just as Dwight, he won't take his in the heat, no use in beating it to death to try and get a new fast time out of it until you get into cooler air. That is if you've gotten a fast time out of cooler weather already. I'd go if I had the time.
Oh yeah, about the converter, my random tech 3inch cat was barely a year old when I had to do some exhaust work. Well in the process of trying to take the converter off, without hitting it just the thick flange, my internals came apart, so I gutted it. The leaded fuel, as Dwight said, will plug it up so either take it off, don't run leaded, or knock out the internals. I did notice that the car has a much louder whistle and spools a bit faster, but not much. The part I like most is the louder turbo whistle.
Good luck. P.S. I'd listen to anything that old fart Dwight has to say, he's got alot of good brain cells left, all full of good info. ;)
What octane are you running? Are you running the same gas now that you were running with Red's 24 degree chip? an 18 degree chip is really low for "Good race gas" I would rather have a little more timing, and less boost than 27# if it were me. Though I don't think a cat is a good race item, at the level you are running I doubt the high flow cat is hurting you that much. Easy way to find out is just take it off and run the THDP open. No need to destroy it by gutting it. (Make sure you back the boost off though or you may then be in NUCLEAR boost territory with the loss of backpressure.
If your FP is good at wot then you are left with either soft valve springs, (still my guess), a flat cam, or possibly misfiring under high cyl pressure. You might try closing the plug gaps up to around .032 and see if that helps.
Since your rpm is going flat above 4000 or so, and not climbing but mph staying the same, I can see NO reason to blame this on the transmission or torque converter. You mention that it shifts into OD at 4800. Just put it in D and it wont shift into OD till you manually do it. D with 26 " tires will still take you at least another 10 mph in the 1/4 without buzzing the motor too hard. I go through at 53 to 5400, 3rd gear, locked up on the converter and run around 118.
So there is no reason to leave it in OD in my opinion. Again, turn the boost down a bit, till you get things figured out. 27# of boost is usually reserved for guys in the LOW 11s or high 10s. No need to punish your car at the level you're at now.
Good luck,
Dwight
Just thought of something, and while it won't really help, it may make others notice something. About his boost levels, yes 27 is high I agree, but he is running one of RJC's Power Plates, so that coupled with the 112, then it may not be too high. Another thing is the low timing his chip has, but again I agree with Dwight, I'd rather have more timing and run less boost.
Scott
Regarding valve springs. These cars arent Chevy's. Don't put in any stronger valve spring than you need or you will kill the cam for sure. There are enough flat cam stories out there to fill a library. Though I am not a big fan of Comp Cams, the do make a valve spring #979 if I remember correctly that is a good replacement for the stocker. Any of the vendors also have their favorites they sell also. Just be warned, all "LT1" valve springs are not the same. Lot's of guys use the old LT1 valve spring with good luck, but just as many have got them that had too high a seat pressure and ended up loseing a cam lobe. Personally to be safe, no matter what spring I bought I would have the set checked by a machine shop for the installed height pressure. I've seen "sets" that varied by as much as 20# from their advertised rate. I think the 979's were around 85 to 90#. Considering the stock cam is out of breath at 5400 or less there is no reason to put a 110 to 125#spring on it, and good reason not to. High spring pressure will KILL the cam. Also, your 60' leaves a lot to be desired, combine that with the extreme heat which take a serious toll on our cars, and add in the fact that you are running a stock IC (I see no mention of a upgrade there) along with the fact that you were leaving the car in OD allowing it to short shift into OD at4800, I think there is a LOT still on the table with your car. You just need to do some serious tuning along with possibly replacing the valve springs. On a decent 60 degree day with low humidity, tuned properly, and a 1.7 60 ' that combo should go low 12's to high 11s with a test pipe in place of the cat, and good leaded race gas in it. And it will do it with a couple less pounds of boost than you are running now. Another thing to consider is if you are running a stock IC, when you build 27# of boost the outlet temp of the turbo is very high. Squeezing it through a stock neck IC and expecting the IC to remove a lot of BTU from the charge on a 100 degree day. The car may have actually picked up if you would have dropped the boost to around 23# and trimmed the fuel to suit.
This would have given a cooler more dense charge.
Many times, more isn't necessarily better. Tuning these cars around the weather and realizing that high temp and humidity is like racing uphill. It makes bracket racing a T car a real challange.
Back off on a bit, and learn more about the car. Going fast in a GN/TR is a lot like eatin a elephant. Take a little bite at a time, and you'll be ok. Try to take it all at once will make ya choke everytime :^)
Good luck,
Dwight
Test pipes are cheap,15 min install. 27# has to go somewhere, through the cat, no good. They're right, leaded fuel will kill that big$ cat in a hurry. Then when you really need it to get the dreaded sticker its junk. I also agree 18 degrees timing isn't enough, Yea no knock and no power! Maybe it's me, I still don't understand why people RACE with street tires, cats. I know you want to see how good the car runs on the street, but if that's the case leave the 94 octane in the tank and the street chip in. It,s either all or nothing. I would (instead of a tranny) buy 26" m/t slicks, tear that cat off(put it in the parts cabinet untill that time of the year) Turn the boost down (20-22 max for the stock intercooler unless you have the bigger neck) Put the higher timing chip back in, leg it out in third gear and LET THAT RAT EAT!!! let the animal go! All of which after the valve springs, that's a must do! Deffinatly not trying to offend ANYONE, like dwight says "just my opinion"
Oh I forgot, I had good luck with kennebell valve springs, part# KB11001 104# seat pressure. I ran them for 8 years with no problems. 60$ You could also call Tom Allen at Champion heads, I'm sure he could hook you up with the latest k-motion springs.
My .02. I read up a lot about the valve springs. This is what I found, take from it what you will. The stockers were 67#. Supposedly, this wasn't enough. A lot of guys used different variations of the "LT1" springs and wiped some cams. The comp cams 979 (with cups) are supposed to be a "good" direct replacment, and the comp cams 980's (without cups) are supposed to be a "safe" upgrade. The 980's are 91#. I will be putting the 980's in next week on my stock block and turbo (and cam) 87 GN. I will let you know how it goes.
Valve spring part numbers and specs are all list on this site at:
http://www.gnttype.org/numbers/8687pn.html
"LT1" springs is really a bad nomenclature ... before all the nice choices were available from places like Comp, the Chevrolet 1970 small block spring was ALSO USED AS THE PERFORMANCE SPRING recommended by Buick Motorsports (in the PowerSource manual). These have approx. 100-105# seat pressure and about 275# over the nose and work fine with more aggressive cams (I've used them for over 10 years now with no cam problems - YMMV).
Ken wrote ""LT1" springs is really a bad nomenclature"
True, because in the aftermarket LT1 is so generic, it is like asking for a Coke, and getting what ever cola is available. A "TRUE" OEM or replacement spring for a 70 LT1 with 100 to 105# will be fine, as he stated. However, be warned that if you order "LT1" springs from your local supplier you may not get that spring pressure. I've seen a LOT of them go at least 20# higher at installed height depending on who manufactured them, etc.. When used on the average SBC, this is no problem because the base circle of their cam is larger, and they do not have the other problems of lobe to lifter bore misalignment, and sometimes poor oiling that our 3.8 has. Checking whatever spring you use at the height you will install it with a valve spring tester is still the best way to know for sure that you are using the right spring rate for your application.
Hope this helps,
Dwight
Ken wrote ""LT1" springs is really a bad nomenclature"
True, because in the aftermarket LT1 is so generic, it is like asking for a Coke, and getting what ever cola is available. A "TRUE" OEM or replacement spring for a 70 LT1 with 100 to 105# will be fine, as he stated. However, be warned that if you order "LT1" springs from your local supplier you may not get that spring pressure. I've seen a LOT of them go at least 20# higher at installed height depending on who manufactured them, etc.. When used on the average SBC, this is no problem because the base circle of their cam is larger, and they do not have the other problems of lobe to lifter bore misalignment, and sometimes poor oiling that our 3.8 has. Checking whatever spring you use at the height you will install it with a valve spring tester is still the best way to know for sure that you are using the right spring rate for your application.
Hope this helps,
Dwight
oops, sorry for the double post
Dwight
Thanks a lot for your advice guys. One thing i did notice, but maybe didn't clarify (before i buy the springs):
At 4100 rpm and 4200 rpm when there is no change in rpm...i GAIN 9 mph total. That is what is throwing me off i guess. The Speed graph is a constant nice upwards curve and the rpm graph holds flat at those 2 rpm ranges, but the speed still increases. To make it worse..2 seconds after im already in 3rd gear on my way to 12.80's, i can see my rpm's DROPPING by as much as 75rpm then coming back up. I sure hope it's as simple as springs!
I've put some thought into it overnight, and picked a few more brains and here's something else i think might cause it:
My car is shifting too soon, and the shift recovery points are not in my powerband. Therefore right after a shift, the car stays in a "lull" until it eventually gets brought out of that range and starts accelerating again. Maybe manually shifting at 200more rpms per gear would eliminate this 4100-4200 "lull" and bring me into the powerband in 3rd again.?
Either way - thanks for the link to the parts, Ken..never found that myself
Dwight and scott and everyone else - I agree 27# is a LOT of boost - i wont run that when I get the correct chip in. I was just trying to see how far i could go until i got knock. I'll try removing the CAT first, then try springs, as well as try manually shifting to drive at a higher rpm. If nothing changes, i'll go with the springs, then work from there.
Thanks for all the help guys! I'll post back and let yous know what the cause was if i can nail it down and fix it.
FWIW, manual shifting the 2 to 3 shift at 52 to 5300 has always been worth a tenth or more to me. With my Dan Boxdorfer modified D5, Locking up the converter with a switch so it's locked from 2nd apply thru the run, was also worth another tenth. These results vary from car to car though. It depends on the combo, and tune up. (Be warned, locking the converter for the full pass is not a method approved by the "be kind to your 200r4 internal parts" society ;^)
I figure that if a 50 cent switch, combined with shifting manually can give me 2 to 2 1/2 tenths, It's the cheapest ET reduction I've ever seen with these cars. (Till something breaks ;^)
Good luck,
Dwight Hayden
Dwight, you seem to know a lot about these cars and since I just got an 86 GN, I hope to pick your brain....that is if you don't mind....8^)