fast82z

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This is a comparison of two logs, one with the block plates in, and one without. I'm surprised how similarly they spool on the trans brake, but seems the block plates respond like crazy given some rpm vs without them.

fast82z

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With these twins out at the track, best it can do is 3.6psi and 3600rpm on the trans brake and takes all of 1st gear to reach peak boost. Just for the heck of it I piped it to run only one of these, and 16psi and climbing in 2 seconds on the trans brake riding the 3800rpm limiter like crazy for 1 of the 2 seconds. Not super happy with the exhaust back pressure since it's at 19psi to make that 16psi in the intake, but we'll see how it goes tomorrow at the track.

I've eyeballed up some 67mm turbos that cxracing sells with the .68 a/r and smaller turbine wheel, thinking I'll probably end up gettin me a pair of those.

On the plus side, I'll have a pair of turbos really good for a single application...like on the 2000 silverado tow/plow truck with a 5.3l, and maybe on another vehicle too.

project89

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19psi ex vs 16 psi in the intake is actually really good. in an ideal woprld u want a 1:1 ratio but ur afully damn close

fast82z

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With those pressure numbers, that's just at 3900rpm on the trans brake so I'm sure it'll get worse when i wind it up to 6800+...aside from the fact that this turbo alone wont be able to keep up the boost that I've been running.

I just got the exhaust pressure sensor in there a couple weeks ago now, and with these twins it showed 16psi exhaust for 21psi intake through the traps at like 6300rpm or so. Running mid 10's at 133-139mph just isn't fun with 1.7x 60' times. Gonna borrow my old 325's from my buddy and probably take a look skyward for the first time in like 3 years.

fast82z

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Didn't have enough tire 275/60/15 to stick down a good launch, but had it banging on the 3800rpm limiter and still made it to 4000rpm and 17psi. Exhaust pressure is insane holding pretty steadily in the 32 psi area all the way down track. It can make about 17psi just after a shift, but tapers off to 11ish just before a shift. Also had cyl 1 and 8 melt off half the ground strap from the plugs, but still compression test just fine. Because of this, no proper 1/4-mile time.

So, twin 67mm turbos are on the way with turbine wheels of 74.1/64.6mm and .68 a/r instead of the oversized 87.4/77mm 1.05 a/r that my current turbos are.

fast82z

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So I tried twin 67's with .68 a/r p-trim exhaust sides and they work fairly well, but I want more. I can get 5.5-8psi in about 2.5 seconds on the TB and they spool to peak boost pretty quick. The bad thing is that at the same boost pressure, it pulls 6-7mph less than the gt45's. This comes mostly from exhaust pressure since the smaller ones hold 25psi in the headers where the gt45's are only at 15psi. The solution for both of these problems is what I've been avoiding, but here is the beginnings of what will be a compound turbo setup:




I had the last setup made to easily convert to running only a single turbo, and running one of the 67's got me 14psi in less than a second on the TB. I also might try out with this setup a 76mm .96 p-trim turbo I borrowed from a buddy. The atmospheric turbo(s) will be mounted in the rear of the car and be either the gt45's or the 91mm Precision I was using a few years ago. The deciding factor being if I happen to sell the 91mm or not. If you haven't asked yourself this yet, yes my barn is freakin turbo mania with all these things.

project89

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are u suing a 2 step on the transbrake?if not a 2step will get u much higher boost on the line and do it much faster then just spooling against the transbrake/converter

fast82z

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I haven't tried using a 2-step recently, but I've tried it in the past and it never made it spool better probably because the bigger problem is the motor just isn't spinning fast enough since the converter stalls around 3000-3200 until a good bit of boost comes in. Plus compounds work all the time so it's much more fun to drive. Also, if I have to let off the throttle and get back in it down track, boost will still be instant.

TwinTurboROC

Nice setup(s). Why are you stray away from running quick spool valves?

fast82z

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The quick spool valves didn't really help it get into boost much while on the transbrake, and only the gt45's have a twin scroll housing for that to have any functionality anyway. Having instant boost using a single small turbo is just great along with the constantly singing turbo is cool, and that frees the atmospheric turbo to have a huge a/r for very low exhaust pressures.

Orr89RocZ

iTrader: (20)

Very interesting setup. Interesting to see the gt45's outpower the smaller turbos just by that backpressure difference. Thought the smaller would spool quicker and get more power down quicker so in the end run faster

fast82z

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Running as you see in the previous pictures with a single gt45 still didn't spool up nearly to my liking. I then put on my buddy's single 76mm with the .68 a/r and still no good, so I swapped in a 67 to that same .68 housing. The 67 got into boost the quickest by far, but the motor still wasn't making power at least mostly from the restrictive exhaust always having more pressure than the intake. I could try the .96 housing on the 67mm, but I'm not sure that will accomplish anymore power and keep up spool.

So since running compounds doesn't look to work in my case, I have to do something to gain power that doesn't involve boost. My problem is that this motor sucks at really anything under 4000rpm. Last time I ran this setup n/a it did something like 13.3 with a 60' of 2.0 or 2.1. Nitrous seems to be the kind of quick and easy answer, but I'm not a big fan of the added complications not only in the system setup and operation, but refilling the bottle also. Since I'm now using e85, I rather like the simplistic functionality of putting more compression in the motor. In the days before I used boost I had my current heads on a 9.8:1 383 with a smaller hyd. roller cam and similar stall speed in a 700r4 that ran 11.4's all day. A D-1SC at 10psi and a more similar cam to what I have now made that 10.0's, and I blew it up the time I tried 15psi. I rebuilt that with 8.5:1 pistons and while driving without the blower I noticed a HUGE drop in power particularly below that 4000rpm mark. So, some flat top pistons will take me from 8.5:1 to 10.5:1. Then I'll run the twin gt45's, and from what I've seen with them so far it should only take 15-18psi to run around the 9.0 e.t. I'd like to be at with the easily available stupidity setting to overrun the 8.5 chassis cert.

I also swapped in an entire new set of valve springs since I've already replaced 6 of them this season, and there were 2 more broken when I did this. I assume this to be fatigue since I think they are something like 3 years old and this cam runs them within <.05" of coil bind, although the inner springs that are doing the breaking don't bind for another like .1" more than the outters do.

Damon

.10" more travel assuming a flat surface on both ends of the valve spring. Make sure you take into account the "step" that the inner coil rests against on the retainer.

Just thought I'd mention it. I've been working on turbo combos all summer but I'm still not nearly experieinced enough to advise you on that stuff.

Valvetrain I'm OK with, though.

fast82z

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I made the valve spring measurements with only an inner or outer spring separately installed on the heads, so yes they are TRUE coil bind heights. Good call though, could easily miss that.

project89

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im curious are u open to using say a 25/35 even a 50 hit of nitrous out of the hole to get the turbos spooled??

RaverRacerX

sounds like your combo is a bit out of wack.. what kind of boost controller are u using? the increased static compression will help immensely with issues. the big questions are: what is your ignition timing like and what is your cams timing like? lastly, what are your downpipes?

Orr89RocZ

iTrader: (20)

I have similar issues in my motor now. Heads and cam are large and car has nothing below about 4000. Converter is stalling only 3500 now so it struggles to get into boost. Over winter i will replace converter again but for now i am adding a 50 shot nitrous hit. Hope that can fight thru the 3500-3900 rpm range and let turbos come alive at 4000. It makes me nervous but we shall see how it goes.

With alot of motor and no comp with big housing turbos its hard to spool. Tbrake nitrous 2 step and anti lag stuff is often used.

RaverRacerX

the wrong cam can SERIOUSLY kill you setup. hell, a smaller cam thats tailored to the turbo would do better than a big donkey dick cam.

(i realize i may be just saying things you already know..)for spool you want more exhaust out faster and dont want any air fuel dumped into the exhaust. overlap is your enemy. try a cam that builds up a fairly high amount of cylinder pressure by itself.

another issue could be you just dont have a turbo matched to your setup. a slightly smaller turbo could build more boost more quickly and yea, you could make less power but would ultimately be faster than the "supra'esc" turbo builds. a speedinc likes to use turbos that have roughly the same turbine and compressor size.

fast82z

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I imagine something like this would work, but like I said, I'm not a big fan of the operational complexities this introduces rather than just mat the gas and let the motor work.

I'm using the BS3 as the boost controller with 5psi springs in the gates, and I've done it hooked to either port on the gates so no problems in that department. My timing is at 36 degrees when trying to spool, and tapers very slowly until something like 8psi. The cam is 262/252 @ .050" 116LSA 116ICL, and I've tried even down to 108ICL with no difference I suspect because the 116LSA doesn't really have a "powerband" like one I did the same with before that was on a 112LSA. My downpipes are 3.5" elbows off of the turbines and nothing more.

I've decided that static compression means basically nothing and that dynamic compression is where the target should be. I know someone's going to cry foul, but take sport bikes: a zx10r has 12.5:1 compression and runs on pump gas...because the cam is huge and actual cylinder pressure is still in the "safe zone" as well as other factors I'm sure, but mainly the cam.

project89

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dosent bs3 have an antilag feature ? set high rpm limit 200 rpms below launch rpm set the low rpm limit about 700 below tha. 10* atdc timing with the spark cut and i bet u them twin gt45's spool up hard

project89

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much smaller turbo but u get the idea
0-15 psi @ 2,200 rpms in about 1.5 seconds

http://www.streetfire.net/video/bad-...ro_2034246.htm

project89

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looking at the bs3 tuning software i see starting line timing table but no option for a spark cut. some really retarded timing would generate some heat in the turbines and should get them to spin up.

i would imagaine the bs3 does have the antilag feature somewere thoiugh, this is the first time ive looked at the bs3 software so im prolly missing it

fast82z

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Anti-lag is in there, but that's for use with manual transmission setups. I've tried and all it does is kill power so that it stalls the converter even less or even shuts the motor down. They even say in the BS3 manual that anti-lag is for manual trans and that autos should just use as much timing as possible.

project89

iTrader: (1)

antilag can be used for either manual or auto, what are ur settings like when u tried it.

an auto with antilag wont want 10*atdc but somewere around 10* to 0 btdc should work. u will have to play with it but i see no reason once u dial in the antilag feature that those gt45's shouldnt spool up hard.

i use antilag with my auto in my tt iroc and it works perfect

RaverRacerX

it shouldnt kill power. many many many people can and have used it to go fast with an auto. how much boost were you making on the antilag?

also, 262/252? holy christ thats big.

fast82z

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It was lucky to make the same or less boost using the antilag as it did without it. I got the motor all put back together and in the car, so soon as the weather comes around I'll get to do some break in before finding out how much difference going to 10.5:1 makes.

fast82z

iTrader: (1)

Pretty much at a closure for this now. Smaller/less turbo would show higher psi sooner, but didn't really produce power in line with the boost since the exhaust pressure was up as well. I also wasn't liking the idea of power being so dependent upon boost, such as having enough boost to launch with. I was seeing two choices left for me. Could have either gotten more launch rpm by way of a higher stall or by making more power when not in boost. The valves needed a good clean up, so with the heads off I put in some flat top pistons to move from 8.5:1 up to 10.5:1. The low drive pressures of the gt45's brought me back to using them as twins. I've been burning e85, which helps allow compression like this with boost. Quite pleased with its first few passes running a touch rich and little low on timing. It spun every launch, while still managing 1.5x 60's, and clicks off 10.0's@ 136 from the 7psi my new twin 60mm gate springs hold it at. I upped it to 10psi, and had to do some heavy pedaling through 1st gear, but came out with a 10.1@ 140. This also maxes out the 95lb injectors, and I plan to put additional injectors up stream to supplement as well as aid in air charge cooling. Something I wasn't expecting is that even though it stalls the converter higher, spool up is actually pretty lame as it launched on average with 2.5psi.

Genopsyde

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Have I ever told you that you're insane? lol.