dyno'd my car, numbers kinda screwy. Cam wrong? Turbine housing too small? HELP!

[fieroX]

I have an SMC alky kit on it already. My intercooler is so effecient that on a cool day, the alky drowns out the spark and it runs like crap. Now on a warm/hot day it works great.

As for the cam ideas, thanks for the info, but there hasnt been a whole lot of research done on advancing/retarding cams on these engines, and last i heard someone was fooling around with it and bent a valve on a piston. The clearances are pretty tight. Ive emailed Ed Curtis, he is going to get back with me soon hopefully, and get me some specs for a cam that will work with my application.

 

[postal]

As for the cam ideas, thanks for the info, but there hasnt been a whole lot of research done on advancing/retarding cams on these engines

There has been alot of research done on turbo cams. They like wider LSA's to minimize overlap and to delay the intake valve opening and closing events. Both of these have to do with the high back pressure that only turbo cars see. Once again you have a turbo specific ground cam and you basically have it installed completely backwards.

With the cam specs you listed and the Intake CL that you have it installed at, advancing the cam is where you could run into valve to piston clearance problems. Retarding the cam 7 to 8 degrees should help to make the car run right and should actually give you more piston to valve clearance.

Ive emailed Ed Curtis, he is going to get back with me soon hopefully, and get me some specs for a cam that will work with my application.

The cam specs you list on your current cam are a little big but it should work if its installed at the right Int CL.

My intercooler is so effecient that on a cool day, the alky drowns out the spark and it runs like crap.

What size nozzle/nozzels do you run on the SMC kit and what pressure do you have the pump set to? Alky will want more boost or timing in the motor when its spraying. If you're spraying too much it just won't run right. I prefer to drop to smaller nozzels than lower the pressure to much. The nozzels are cheap and Steve at SMC sells them for about $5 each. You should be able to use the alky to get more timing into the motor. I believe your 3800 has a very similar combustion chamber as the FWD heads on the turbo trans ams. That should make the two cars like similar timing levels. Getting the timing into the 23 degree range should help get it to run the way you want and should really help the 5000 rpm and up power output. 23 to 24 degrees seamed to be a good comprimize of total timing and the amount of boost I could run w/o detonation.

I run a liquid IC on my TTA thats supposed to be a little better than the one your running. The liquid IC will make the car more sensitive to how much alky you can spray. It will make it harder to atomize the alky. Pump pressure has alot to do with how well alky atomizes so thats why I like to keep the pump pressure up and drop down the nozzel size. You can have enough IC and enough alky spraying to get ice in the up pipe. You just have to trim the right amount of fuel and add the right amount of timing to get it to run right. When you get it set up right it will go from some thing thats bogging the motor down to some thing thats allowing you to make 50 to 100 more HP.

My exhaust was glowing after 5 seconds of WOT for god sakes!

The air and fuel mixture burning in the exhaust system will make a pair of cast iron exhaust manifolds run so hot and glow so bad that they will look transparent! The low timing advance you're running coupled with the exhaust valve opening too soon d/t the Int CL the cam is installed at could have alot to do with this.

Theres some good advice here, take it or leave it.

Jason

 

[fieroX]

thank you postal for all the information. As for nozzle size, Im not sure. Just the one that comes with the kit. Im only running like 17 degrees of timing right now, so maybe that will help out some. And ill look into retarding the cam some, right now its installed straight up. I have a fully adjustable timing set so I can go up to 9 degrees either way. Thanks again for the ideas.

 

[postal]

Steve sells a little kit to turn a single nozzle set up into a dual nozzle. I think he sells that upgrade kit for around $25 or so. The standard single nozzle size is a #15. I "think" that is a gallon per hour rating. You may want to try a pair of #5 nozzles.

I'm a firm believer in running a cam straight up. If you go buy an off the shelf Edelbrock or some thing for your SBC. Running a cam like that straight up will more often than not be the best. Now when you have a custom cam ground they some times have to grind the cam advanced or retarded to fit the lobe profiles and the LSA you picked within the coarse ground lobes of the core they used. BTW I just went through this when ordering my cam for the stage 2 motor I'm putting together. The specs you listed look like the cam was ground advanced. This means that when the cam is installed straight up the lobes are actually advanced. It looks to me like your cam would be considered to be ground at approx 7 degrees advanced.
With the .050" specs you listed of:
Int dur: 226
Exh dur: 220
LSA: 116
Int CL: 110
This would have your .050" timing events of:
Int open @ 3* BTDC........******
Int closes @ 43* ABDC
Exh opens @ 52* BBDC
Exh closes @ 12* BTDC
Int CL: 110*
LSA: 116*

****** This shows the intake opening while the piston is still on its way up. This is where piston to valve clearance could become a problem. Advancing the cam would make the intake open even sooner and reduce the clearance even more. Now retarding the cam as above will make the intake open later and the piston will be on its way back down before the int valve hits its .050" lift point. This will not cause a problem on the exhaust side because the way its installed now or if you retard it the exh valve .050" closing point will still be before the piston hits TDC. Retarding the cam 8* would make your .050" timing events look like this:

Int opens: 5* ATDC
Int closes: 51* ABDC
Exh opens: 44* BBDC
Exh closes: 4* BTDC
Int CL: 118*
LSA: 116*


What is a stock GN or TTA exhaust housing considered? Would it be considered a 3 bolt T3, a T4, or something inbetween? I got all kinds of caught up in cam shaft specs and back pressure stuff for this stage 2 project. Turbine wheels and housings will have a huge effect on the proper cam shaft selection. What turbine wheel do you have on this 66, is it the P-trim wheel?

HTH: Jason

 

[fieroX]

now that you metion it, i believe they told me it was ground advanced. (for some reason 6 degrees sticks in my head) See my cam is a regrind from Erson, ground off a stock cam. I have a .100 longer pushrod to offset the difference.

My turbine is a T3 .70 a/r V-band discharge. P trim turbine wheel yes. I have a .84 a/r turbine T3 i can try though, but i was just affraid of the larger turbine making it lag more than it already does. What will retarding the cam 6 or 7 degrees do to the bottom end power? I bet i can go 4 or 5 more degrees which down low may help power. Maybe even go 6-8 more degrees down low. Ill get my computer guy on here.

Thanks for the info man.

 

[postal]

On a naturaly aspirated or supercharged motor retarding the cam would hurt bottom end power. This is because you closed the intake valve later and therefore bled off some of your compression. Neither one of these two motors had 30 to 50 psi of back pressure in the exhaust manifolds like the turbo motor will. The exhaust back pressure being 20 to 30 psi higher than the intake manifold pressure is what makes the turbo motor like a cam with a wide LSA and a later intake valve opening point. Your trying to minimize the amount of trapped exhaust gases that POP into the intake manifold when the intake valve opens. You're also going to try to minimize the force that it pops into the intake with. This is very similar to they way a really big cam craps all over itself at really low rpms. Its magnified on a turbo motor and will still occur at an rpm level where the big cam NA motor had itself cleaned out. This is because there is a much higher pressure difference in the manifolds of the turbo motor.

For your motor and cam combo retarding the cam should really help minimize the reversion and the gain from that should really help minimize any low rpm hit from it.

BTW: What rpm range and shift point are you wanting to run your motor at?

I have a .84 a/r turbine T3 i can try though, but i was just affraid of the larger turbine making it lag more than it already does.

I'm going to be running a 252" motor with a pair of ball bearing P-trim turbos that have T4 4 bolt .69 a/r turbine housings. I have a wet NOS set up thats jetted to 50 HP that I may have to use to help spool them up. You would be suprized at how much a small and safe amount of NOS kicks a turbo in the butt. Its like hit the switch..."one thousand one"....boost gauge shoots up! Throw in a little $15 hobbs switch to kill the NOS a few pounds below your set boost level and you have a nice safe fast spooling set up.

Jason

 

[fieroX]

ive got it set to shift near 6100 rpm. I had nitrous on it for awhile and actually dynod with it. A 50 shot only made 30 wheel hp, so I felt like it wasnt doing anything so I took it off. At that point I went from a stock stall 1500 rpm, to a 4000 stall which helped the launch a lot. I figured with the correct tuning and such I wouldnt need any nitrous to get this thing to launch like the supercharged days. I can get it to stall a bit better now that I have my brakes fixed. Last season they were sucking real bad, and I couldnt get it to make any boost off the line without pushing through the brakes. Now it will hold 4 to 5 psi of boost and it launches tons better. Any more ideas?

 

[fieroX]

postal, check out these cams and let me know what you think of each profile. See right now not alot of research has been done with series II engines running turbo. the only experience to go off of is GN experience and those engines are different animals altogether.

http://www.stattama.com/index.cfm?fuseaction=browse&id=21413&pageid=37

Thanks man.

 

[TurboTR]

That is a nice project you have there- would love to be able to help out on it personally!

Now wait a minute- from the website:

"We started off very conservative- 15 psi, <10:1 air fuel ratio, and stock timing. The first pull netted 379 WHP. We slowly increased boost and timing advance as well as lowering the WOT ICCU setting to lean it out a bit on each pull. We also switched from 2nd gear to 3rd gear pulls after a few runs because the motor was revving way too quickly. After familiarizing with everything, but starting to run out of time, we cranked the boost somewhere into the mid 20s(gauge only goes to 20). At the stomp of the pedal, WHP shot to well over 500 WHP, but inadequate ignition spark quickly became a problem. HP peaked right away and then just fell off very quickly. Since converter flash was a factor in the peak WHP number, it should be taken for what it's worth. Rick does not wish to claim any kind of record with this pull, and neither do I. Especially because the pull was terrible over-all as power fell off quick.

IMO the words "very conservative" don't apply here if the above is true. If you really have the stock timing curve in it, yet are running like 10+ more boost now than stock ever saw that is a recipe for disaster, asap. Especially if the part about adding even more timing on top of it is true. Sorry if I'm being too simplistic here, but it seems to me that it could just be that the power curve is so abrupt and wavy from detonation (abnormal combustion) and/or heavy knock spark retard...

"Inadequate ignition" is likely not the problem there... I think it may be just falling on its face from inappropriate tuning. FWIW, mine for example has the oem stock Buick ignition, including the stock coilpack, and I run a T76 turbo with 30+ psi boost on it, + up to a 175 shot of hose on top of that and it still hasn't missed a beat. Fresh plugs gapped at 0.28". Is it optimal? No. Does it work? Sure seems to. Surely your type 2 can ignite ~ 20 psi, assuming you have good plugs at a reasonable gap.

As for backpressure, I used to run a .63 4 bolt hsg on it because it spooled better at the time. The car went 133+ mph with it just rolling it off the line. A hard launch would have likely been in the 135 range. This with a 235" S1 motor at 3650 lbs race weight (no hose, etc back then, almost 10 yrs ago now). I measured the bp at 50+ psi. Swapped hsgs to a .81 a/r and could not really measure a bp difference; very crude measurement technique though, I admit. The old q trim exh wheel is just not as good as the current GT wheels. Moral of the story, yes you will have bp no matter what you put on (within reason), and no that is propbably not what is destroying your power curve, even if teh cam is slightly out opf phase. Personally I agree with Postal on the cam stuff, but OTOH turbo Buicks seem to still run quite well with probably worse cam settings in them...

Hope that helps some...

TurboTR

 

[fieroX]

Originally posted by TurboTR
That is a nice project you have there- would love to be able to help out on it personally!

Now wait a minute- from the website:

"We started off very conservative- 15 psi, <10:1 air fuel ratio, and stock timing. The first pull netted 379 WHP. We slowly increased boost and timing advance as well as lowering the WOT ICCU setting to lean it out a bit on each pull. We also switched from 2nd gear to 3rd gear pulls after a few runs because the motor was revving way too quickly. After familiarizing with everything, but starting to run out of time, we cranked the boost somewhere into the mid 20s(gauge only goes to 20). At the stomp of the pedal, WHP shot to well over 500 WHP, but inadequate ignition spark quickly became a problem. HP peaked right away and then just fell off very quickly. Since converter flash was a factor in the peak WHP number, it should be taken for what it's worth. Rick does not wish to claim any kind of record with this pull, and neither do I. Especially because the pull was terrible over-all as power fell off quick.

This is not my situation. This quote is from another guys turbo project.