dr_hunt Posted August 12, 2006 Share Posted August 12, 2006 I would think that the converter would not kill driveability that much over what you have now since when you start making boost the converter slips more. What the converter people are going to want to know is what launch rpm is your target and what TQ you'd be making at that rpm along with what TQ you'd be making at a lower rpm like 4500 or even 5000. As an example the converter in the z is a 4000 stall for a sbc. On the brake I can stall it at 4300. Just depends on the TQ of the engine. So as your boost builds the stall rpm will increase until you reach a steady state point. My understanding from talking to Art Carr before he built my converter was that the initial stall should be high enough to start making boost and then it will raise slightly into the final stall rpm right before launch. He was talking like a second or two at the most for this to take place. If it doesn't happen that way to send it back and they will restall it until it works right. Driveability of a 5500 stall versus either my 4000 or 4500 stall converters is the same on the street, I don't notice any difference between them. At some point though ted, your car will quit being a street car and become more of a serious car that is track oriented. I say that because from what I'm reading your having problems planting the HP! Geez, what a problem to have! Quote Link to comment Share on other sites More sharing options...
Z-Gad Posted August 13, 2006 Author Share Posted August 13, 2006 Driveability of a 5500 stall versus either my 4000 or 4500 stall converters is the same on the street' date=' I don't notice any difference between them. [/quote'] Well Dr Hunt, I will be calling Precision on Monday to talk to them about my setup and see what they recommend. (They make the funky TH400-2JZ bolt pattern converter that I am using). After some more research, everything that I am reading on stall converters for a 3 speed is to choose a stall around your peak torque, so I may end up with something closer to the 6000 RPM range. This is just making my head hurt, and I am still on the fence about what to do with only a month to go before SEZ!! I'll be making a decision the beginning of the week though. Better your MPH at all? Yes I realise thats unlikely given you were tuning it and all' date=' just curious. [/quote'] Dave - Nope, didn't get to better anything... The car just got the better of me this time. I only made 2 passes with the boost controller turned on, and I had to get out of the throttle after the 1/8 mile due to wheel spin both times. JT - I feel your pain brotha' Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted August 13, 2006 Share Posted August 13, 2006 Mike, IMHO, the best route to go is the converter. However, the 4200 stall is on the edge of not being driveable on trips like to SEZ. With the boost coming on at 5000+, the new stall would have to be at least 5500. You could probably still drive it around town but there is no way you want to make a trip like the SEZ with that. The problem right now is flow and velocity with the engine not under load and I dont think there is a single thing that caused it but all the changes have compounded it. How do you fix it? Is it possible the actual compression with that combo is in the 7s? Tough to fix because how would you know and how do you fix it? Not much you can do with the head so you are stuck with it. The cam could also be a culprit, not so much the lift/duration but the lobe seperation angle. Regardless, I would go back to the 272s as I think that will bring the torque peak down a couple of 100 RPMs. Then there is the turbo/plumbing and intake. As you saw, the boost went from coming on at 150' to 300' when you made those changes. That Q-trim size wheel and .81 housing is another culprit. I would look into the next smaller a/r housing if there is one. Plenty of Turbo Buicks running mid-9s with P-trim/.63 T-72s in 3700# cars. So you lose 30-40hp and 4mph on the top end. 40hp from too much is a nit. You more than make that up in your 60' and dropping 60lbs with wheels/tires. I know you are tired of hearing me preach that :D The easy fix for spoolup is to throw a small shot on it but I am not a fan of that. With the combo you have, the RPMs are going to come up in a blur and it is going to hit hard. Not only will you now break loose off the line, you are going to start breaking parts, IMO. You know what it feels like when it hits at 300' and you already have the car rolling to minimize wheelspin. Now imagine that at rest! If it was me, I would go back to the 272 cams and the smaller housing and see what that does for the torque curve and where it starts bringing on the boost. Only then would I have the converter redone. Probably cannot get that all done for SEZ, so the quickest and most effective gain would be the housing. I have been on your case about tires and I have to admit I am now wincing and saying a couple of Hail Marys every time I see the car wiggling at half track and on the big end. Like Doc said, there comes a point in time when a street car crosses the line and one that has 8-sec potential is definitely one. Like I told you a long time ago, HP is not your problem, its getting the car to hook and leave. Go back and start focusing on that. Your mentor, counseler and friend Remember, the most HP does not always win drag races. Quote Link to comment Share on other sites More sharing options...
Jeff Posted August 13, 2006 Share Posted August 13, 2006 Mike, I bought a car trailer a few months ago that you are more than welcome to borrow for SEZ but I don't have my truck set up for towing yet so I can't lend you the tow vehicle. Let me know if you're interested. Quote Link to comment Share on other sites More sharing options...
JustinOlson Posted August 13, 2006 Share Posted August 13, 2006 I think your setup is solid. I would try the nitrous before making a decision on the converter. You dont want to go to a loose loose converter if you still drive it long distances. It will definitely be a rocket once you get it sorted! Justin Quote Link to comment Share on other sites More sharing options...
510six Posted August 17, 2006 Share Posted August 17, 2006 I am a big fan of nitrous...it`s my first love really.I agree with Scottie that a car hitting a shot of N20 will spool NOW.I plan on running a small shot of N20 just to spool the turbo at the track.I would start with a really small shot and work my way up rather than a big shot and putting your car sideways(ask me how I know).All I am saying you better be ready for a ride when hitting the juice on a BIG turbo car. Quote Link to comment Share on other sites More sharing options...
Z-Gad Posted August 17, 2006 Author Share Posted August 17, 2006 Thanks for the input all. After discussing options with PI as well as Precision turbo, I have chosen to try running a nitrous shot out of the hole. Guys with similar setups to mine in 3700 lb Supras are cutting 1.4x 60' with a 75 shot off the line. Hopefully, I will have it in and be testing by the end of the month to have he car ready for SEZ. I did get to go out and do a little more pump gas tuning yesterday, My low boost setting is 20 psi. That is with the boost controller off, as that what the wastegate is set to. What a blast to drive!! Quote Link to comment Share on other sites More sharing options...
JustinOlson Posted August 17, 2006 Share Posted August 17, 2006 Very cool, I want to see some roll race videos from 50-60. Does the car sound any different under load with the larger turbo? How about at idle? Quote Link to comment Share on other sites More sharing options...
Z-Gad Posted August 18, 2006 Author Share Posted August 18, 2006 I can't really tell from inside how the car sounds, Hopefully we'll get some video of it at the track shortly to compare it to the vid in my sig. At idle, it sounds the same to me and it idles surprisingly well with the Crower 276/284 cams at around 1000 rpm's. Quote Link to comment Share on other sites More sharing options...
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