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Discussion Starter #1
Just built new combo and been having problems making boost , when spoiling it up I can only make 5.5-6 lbs it's a 445 billet head sbf on q16 twin 88 gen 1 promods and leaving at 4500 . I have tried and done and looked at everything and can't find nothing wrong just hoping someone else mite have a idea or had same problem before . I would figure it would make 8-9 easy
 

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Where is your timing at and have you tried messing with dumping timing and throwing a bunch of fuel on the brake to help spool? ...
 

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Discussion Starter #3
I tried all that and still no difference. I've got timing down to about 10* but will make about same with 15*
 

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4500 rpm ought to be singing them turbos.
Don’t pull any timing. What does your timing look like coming up on the brake?
control the iat on Q fuel , what makes it great also can cause problems in the higher boost numbers.
imo , c-16 or methanol ✅
 

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I can tell you there's a huge difference in spool up if you carry your NA timing into boost, vs pulling a degree per pound of boost. On E70 (non intercooled) I kept full timing until 5psi and the spool up was night and day better. I've seen guys say they will keep full timing in until 10 psi on race gas.
 

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I tuned a SBF 448 Neal headed motor for my buddy. It makes 7 lbs at 4200 in less than 3 seconds. It's 11.1 to 1 compression on Q16. The timing is at 36 degrees until 9 lbs. You need timing in it.
 

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I’m curious what timing does. Keeping full timing in it into boost, is that just for getting on the chip against the converter? Is the converter that tight that its hard to get to the target rpm or is it really doing something else?

Boost builder functions seem to like to drop timing once you get on the chip and develop a lb or two of pressure. Some may drop it earlier than that or later. I have a similar issue, bbc with twin 80’s that have a 88/96 turbine. 5-6 psi by 4200-4300 so far. But it takes a good 4 seconds. They are somewhat rear mounted and large 1.32 housings. I still need to play with it but i found that dropping timing down to 15 deg once it hit 2 psi boost really helped it get to 5-6 faster. I think the heat plays a big role here since the motor has no issue getting on the chip even at 15 deg of timing. Converter is abit too loose imo.

But even on the street it doesnt get to boost til high 4000’s anyway. Some combos just wont want to build anything below a certain threshold based on turbine size and housing ar
 

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We often need to keep in mind that there is only so much you can artificially make in addition to what it naturally makes. You need air to turn, but more importantly to accelerate the assembly. Any combination is going to make a certain amount of exhaust product at a certain rpm. You want more turny of the wheely? Raise the rpm. You can artificially get some more out of it by increasing heat in the exhaust path or even creating pops in the exhaust I hear.

My conclusion with my combo is this: The first thing you need is engine rpm. Ya gotta start moving air in and out so the turbo has something to work with. Under low load with looser converters, this means give it plenty of timing and whatever fuel it asks for.(if the converter loads the engine greatly before you get to the two step, you may have to be a little more conservative with the timing) Once you arrive at the two step rpm, you can try the tricks. I have played with timing to the point of even going negative. Anything less than double digits didn't really yield me more boost on the two step with my very limited time I can be on the two step. I also tried adding fuel, and that didn't give me any great results either. (methanol). Some have said that excessive fuel can cool the exhaust charge, which I could believe.
 

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Methanol and high timing on my twin 80mm/96mm turbos, tightest stator PTC makes(12-45) and don't pull any timing until 10 or 12psi(launch boost target). 10psi in 1.2sec from WOT on the brake. This is around 4200-4400rpm. To get to 12+psi I have to add rpm to make more load from converter like 4800-5000rpm with same 36-38* timing.
 

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Methanol and high timing on my twin 80mm/96mm turbos, tightest stator PTC makes(12-45) and don't pull any timing until 10 or 12psi(launch boost target). 10psi in 1.2sec from WOT on the brake. This is around 4200-4400rpm. To get to 12+psi I have to add rpm to make more load from converter like 4800-5000rpm with same 36-38* timing.
Whats the converter flash rpm if you mat it before boost? Is it easy to get up to 4200? Wondering how tight it is
 

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I honestly can't remember but it's the tightest 9.5" PTC can make and has a mechanical diode to try and get all the performance I can out of it. I'm not saying 1.2sec from idle to WOT. I lightly foot brake it into the pre-stage beam to get everything warmed up before going on transbrake and going WOT. I see a lot of people just roll into beams at idle, grab transbrake and just flat foot it WOT. This seems to take a lot of time compared to my method. If I only need to launch on ~5psi I don't even need the bump box.
 

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It is very uncommon for a SB to need a 10" PTC converter especially with only 3.75" stroke but honestly that is what it needs if I is going to use a PTC converter. It's a half billet aluminum, steel cover so it's a pretty big investment to swap to a similar 10" bolt together. I will say this, the Pro Mag 44 made a huge difference in in the overall tune-up and power the engine makes. It took 25-30% more fuel across the entire fuel map to get the WBO2 back to reading the same AFR as the dual coil MSD 8 Plus made. This power increase was very evident trying to get the car to launch without knocking the tires off at every local track I ran at. At the time most class rules were hitting me with a +100LB weight for a SB with a Pro Mag. I thought this was bullshit and said so on many occasions. My thinking was lit is lit and didn't matter what was making the spark. HOLY SHIT WAS I WRONG!! One amp (1A) at the plug for 26* of crank duration is worth a lot of power at a safer AFR. I have found that you can run the engine much harder on methanol vs gas and its happier plus longer life between freshen-ups.
 

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Not to get off topic but i ordered a 12-45 9.5” ptc as the tightest they could get me without going 10” for my 555 bbc. Its nothing super special but seems loser than expected. All motor it flashes to 3600-3700 from a roll. With the turbos it seems to go alittle higher but has no issue getting to 4500 on the brake even with pulled timing. Just making sure i got what i requested
 

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That seems about like mine. They now have a new cover that is supposed to tighten them up about 5% up top which I really need. I am still slipping 10-11% at 8100rpm thru the traps even with diode. That's about 32-33psi with plenty left in it. Now that I have the block poured, heads dry-decked and Fuel Hoops in it I can turn that bitch up!! I think the engine probably makes around 750hp NA give or take, it flatlined my buddy's 48" wheel chassis dyno at 1507RWHP at ~21psi.
 

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Discussion Starter #15
It will spoil up faster not pulling timing but it will not make no boost maybe 1psi. I would of figured this thing would make boost easy but it's been a task to get it to make some and it's 4.100 stroke and 10.1 compression
 

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Guess the obvious is no leaks in the piping on cold or hot sides? Wastegates no leaking or opening prematurely
I guess looking at the obvious is a good place to start if it has not already been done. I have seen tape over the gates be used as a tool. Can use at joints too as a witness.
 
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