MY99TAWS6

iTrader: (3)

Well if compression is not bad and you are not seeing oil would think leakdown won't show much. If you have proper fuel now and ignition is working then thing should make pretty good power. I would not expect my 408 NA to put out much more than 450 rwhp and maybe 450rwtq. After all Na it don't have headers but is breathing thru stock type manifolds and its lowered to 9.5 to 1. Cam is pretty mild really and not sure how much power the afr 225 which was worried would hurt low end are doing. Expect a bit from the fast 90.

But mine is strong low, very strong off boost but also my boost comes on likely in the 2000 range have to run some logs but seems like full boost at 3000 or so.But of course twin front mounted turbos dont hurt either.

I would get that car on dyno and look at the numbers and see what it shows.
I wish had chassis dyno in my city. no such luck.

98Z28CobraKiller

iTrader: (17)

I didn't take it wrong. I knew what you meant and I can only imagine your frustration. I have been following this for some time.

Moving the turbo forward will help alot. EGT's being low is pretty tricky though. All the plugs look the same? wires all look good? have you metered them out?

Casey2323

iTrader: (14)

Call Circle D .. or send me your Info and i will call Chris myself... So i can get the exact specs on your Stall... 2500-2600 is no account... again my Guess is either a 1A or 1B ... Bolth are REALLY tight... Being able to losen it 500 would help a TON ... I test all of his stuff ALOT... I would like to know what the specs are exactly....

Texas_WS6

iTrader: (9)

Two different set of new MSD wires, and probably three to four different sets of plugs. Reading the plugs they show to be lean, due to the second fuel pump not coming on. I would expect them to show way fat now.

Texas_WS6

iTrader: (9)

I have the build sheet on it. I will look at it tommorrow and post up what it has in it. To tell you the truth, I like the stall speed while driving. It does stall, when the convertor clutch locks it locks up solid, hits like the 1-2 shift hits, and feals like a 5th gear. Looking at the scan, when it shifts you can see it is stalling nicely. I really think there is a problem with the 408 not making proper power down low, this would make the convertor seam tighter then it is. I would hate to send it off and have it loosend up before finding/fixing the lack of power in the 408 before boost. I say this because this issue exsisted with the 4L60 and the 3500 stall, and after the stall was rebuilt/loosend up to 4400. It leads me to think the issue is not in the trans or the new convertor. This 408 has never made the right power. There is something going on with it, I just can not put my finger on it.

Texas_WS6

iTrader: (9)

Can anyone tell me what the compression ratio should be on a 408 with -12cc reverse dome pistons and 70cc head chambers? and what the compression gauge should read with a VTC-3 cam set up at a 105 ICL, with that compression?

Zombie

iTrader: (2)

Here are some observations of mine since we are in similar air conditions.

I have tuned a few 408's here in Vegas where we also can see summer time DA's of 7000'. Most of the full weight 408 F-bodies only manage to run mid 11's @ 115-117mph. I've also never seen one that made more than 460 RWHP SAE and that usually involved a 10-13% correction factor bringing it to 414 RWHP.

Bad air KILLS power. In summer LVMS is home of the 14 second LS1. I've seen 1 C6 Z06 break 120mph and I've watched 5+ of them run, most of them modded.

Texas_WS6

iTrader: (9)

Yeh, a stock ls1 f-body runs 14.2-14.5's here.Last time out there was a pissed off fellow with a TSP tuned 408 only hitting 12.7's na. There could be an issue with my cold air piping, there are allot of bends in the piping, and it is 2.5", that might explain the 22# sprung waist gate = 12 psi of boost, I guess even though the sensing line is run to the manifold, the turbo might be seeing 22# at the compressor housing. To tell you the truth, I am pretty much sick of the lag/problem. I am about done trying things and I am pretty much ready to just move everything up front. Nothing I do seams to help this lag issue.

Zombie

iTrader: (2)

moving it up front will definitely improve responsiveness. Thin air means more lag and less power, nothing can be done about that unless you install nitrous.

Your converter is way too tight for your setup as a rear mount which doesn't help. It will probably work OK when you relocate the turbo, but you may still need to have it loosened up. I use to have the same lag issues as you years ago and they are frustrating.

Texas_WS6

iTrader: (9)

Well, I got my 2step in yesterday. I installed it tonight and tested it out. It works as advertised. It does not however help me make boost while the Tbrake is on. I am sick of this lag! I am pretty much ready to throw the rear mount stuff away (or sell it, I am sure it would work right with a smaller turbo then the GT-88) and start building a front mount setup for my GT-88. I have done everything every one has sugested to make the lag go away. I am not going to spend any more money on trying to get the rear mount setup to work with the GT-88. I will have to wait until Elk season comes and goes first. I have to get one of my 3 FJ-40's going for the hunt, and my wife will not camp so I have to rent a dang cabin for a week! After Elk season I will start again on the turbo move. I will just work on the tune the rest of the summer.

It is much cooler tonight, probably 85-90 degrees, and the engine coolant temp is staying around 205. That is not exceptibale. I have a 160 degree thermostat in the car and a Be Cool radiator! I will never waist money again on any Be Cool product! I will contact Griffen next week and see what a 600+hp custom radiator will cost me.

I want to thank everyone who has tried to help me work threw this year long battle. I sure wish something would have worked to make this lag go away. I am sure moving the turbo to the front will fix the problem.

MY99TAWS6

iTrader: (3)

So you experimented with various settings you might have to go higher or something.
With the brake you should be able to go higher than you can just footbraking.
But of course if that don' work I guess its time to go front mount if you don't want to go
different turbo.
One option left is nitrous . Small shots can do wonders.

Texas_WS6

iTrader: (9)

I was thinking about it this morning. My convortor locks pretty early on the Tbrake at 2700 so I set the 2 step to 2500. I think I will play with different settings on the 2step while in nuetral and see if I can find an rpm that the turbo starts to build boost at. I have to send the convertor back to get it loosened up, might as well find with the 2step the rpm the 2step makes the turbo build boost at, and then set the convertor up for that rpm.

98Z28CobraKiller

iTrader: (17)

Unfortunately, that isn't how it works. With the converter as tight as it is, you cant raise the 2 step over the tbrake, You wont be able to find any boost. The converter needs to be loosend to 4500 (regarless of where the turbo is mounted), by about 3500-3800, you should start boosting on the 2 step. Might take a couple seconds. Then you set the 2 step as close to the stall RPM as you can get, and still be able to hook.

Texas_WS6

iTrader: (9)

Yeh, I know when on the tbrake I can not get over what the convertor, but I can still activate the 2step in netraul without activating the tbrake. Wouldn't this be acting like M6 car as far as the 2step is conserned? Won't the 2 step (set at the right rpm limit) make a M6 car build boost with the clutch engaged? I am not doughting, I just thought that is what the M6 guys do. I might be mistaken. If that is what they do, then I figured I could imitate this by placing the trans in neutral and play with the 2step to find what rpm the 2 step will cause the turbo to spool up, then I would have an educated idea on how much stall I need. I really do not want to put a 4500 stall in it if I can do the same thing with a lower stall.

Do you think the way I want to test it will work?

Do I need to do something to the tune to help the 2step make the turbo spool up?

Thanks

98Z28CobraKiller

iTrader: (17)

it'll work in nuetral but it wont be usefull data because there is no load in nuetral. That's why they retard the timing on the 2 step in the M6 cars to create artificial load.

Texas_WS6

iTrader: (9)

Hummmm, I guess I can do the same thing and retard the timing, but like you said it might not be usefull data, unless It still will not spool the turbo. I guess if I do this and the turbo still will not spool then I will know there is nothing I can do to make the rear mounted GT-88 work right.

MY99TAWS6

iTrader: (3)

M6 cars use two step and antilag to good effect. Some need the antilag and usually you won't get too much boost on just the two step with the auto.
Autos dont' need antilag much at all. I can quickly build boost on my footbrake with my two step its set to 3000 and going to lower it a bit as it does try to pull thru the brakes. Also changing to bigger turbos shortly and might have to play with settings some more after that. I am running the PY3400e stall converter.

As said its also very common with the import guys to run small shots like 50 shot of spray to help spool up big turbos. I am going to a big turbo in my auto talon race car and may find have to run shot as well.

You can likely keep messing on this forever changing converter, two step rpm. But in the long run you probably should just move the setup to front and then hit it with small shot if need be. You don't need a fancy direct port kit like I got.That was mostly for car show and raising the hood intimidation effects.
Just a simple nitrous kit wet or dry will do the job well.

98Z28CobraKiller

iTrader: (17)

I have no experience spooling a turbo M6 car on a 2 step but I believe that you will end up having to spin the motor higher in nuetral to see boost than you would with the tbrake. Like alot higher.

Also, you should ride in a car with a 4500 stall. I bet it feels different than you would think. Mine is right about there and a passenger cant tell at all when cruising around town.

MIGHTYMOUSE

iTrader: (59)

hate to say this but everybody that i have ever been in touch with running a built 4l80 is either having tq converter problems OR is running a yank 3400.


brands aside if you cant get past 2800 on the trans brake the problem is all converter.

i agree you may have some compromises in the system but if it pulls hard up top i wouldnt abandon the powerplant or power adder JUST yet. get a MAJOR restall or just call yank.

Texas_WS6

iTrader: (9)

MIGHTYMOUSE! Long time no see man! Were the heck have you been? I haven't seen you on here in a long time. I bet I was just looking in the wrong place.

Yeh, once under 12psi of boost this thing pulls very hard! I have no way to describe it. You can be running 80mph and stomp on it, once the rpm hits 5000 it just changes from one car to another! It pulls as hard at 80mph under boost as it ever did with the 150 shot at launch! If that makes any sence. I have never felt a power adder pull so dang hard on the top end as this thing does!

No I will not throw out the 408 or the turbo. I am afraid it will have the 3-4 second lag time as long as the turbo is in the rear of the car. Looking at the log files, it looks as though it does not matter what gear it is in or if you are sitting still or moveing at 80mph, it will not build boost before 5000rpm. Once it makes boost it will hold it for the rest of the run.

I can go ahead and send the convertor back to Circle D and have it loosend up to 4000 or 4500. I was afraid that if I did, it might need a different stall setting once the turbo was moved up front. I guess thats what the 2step is for, to limit the launch rpm so I think I will call Circle D this week and let them know I am going to send it in. I have been in contact with Chris, he knows what is going on and agrees the convertor is too tight. Man this thing drives around like a dream. I trust Chris at Circle D. I know Yank is good, but I feel like Circle D is too. I know he will work on it hard to get it dialed in just right for my combo and never complain about it to me. He is very easy to work with and has great customer support. I know Yank convertors are excellent convertors, but I am going to stick with Circle D. They too are a top notch convertor company.

So for my setup (408, L92 heads, VTC-3 cam, 10:1ish compression, 3.7gear for now but going to 3.2 or 3.0 gear latter, 4L80 stock first gear ratio, heavy car, rear mounted GT-88 turbo for now with plans to move it up front latter this year), what stall speed should I try and get the convertor too?

Thanks for all the help guys, and MIGHTYMOUSE, glad to run across you again, hope to see you here more often.