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Discussion Starter #1
My setup is
351w stock stroke
tfs tw 205cc heads
vs racing 7875 p-trim
tfs stage 2 cam
3.5inch downpipe
tremec 5 speed

My question is the car feels slow on the bottom up until 3500rpm almost as if there is a delay, then it pulls really strong. Coming from a vortech setup the car just doesn't feel as snappy, is this what turbo lag feels like? In first gear it doesn't even spin the tires if you stab the throttle like it did with the blower.
 

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Yep, that's t-lag.

ks
 

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I wouldn't expect any lag with that turbine and your cubic inches. The cam isn't the best pick but I would still expect it to be rather quick getting into boost. The TW 205 head will support 1300+hp. What's your static compression ratio and target boost? Was the engine retuned after the blower was swapped out for the turbo?
 

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i was kind of thinking the same...my mostly stock 5.0 will spin the tires without dropping the clutch in 1st gear. I dont know what power range is on that tfs cam....but seems like some kind of tuning is needed...

good luck.
 

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Discussion Starter #8
I am tuning with Moates Quarterhorse. The tune thats in it only has 18 degrees in it on the WOT table. So that could be why its so lazy on motor bc of such low timing. I will switch over to the sea level spark table so I can put in more timing in on motor before I get into boost. I was just using this method to be safe on the first drive. As far as compression it is 9:1, the short block is just a freshened up short block from a f-250 (rings, bearings, and set of speed pro hyper pistons).

The top end defiantly feels better than when I had the blower. Just bottom end before 3500 rpm feels real lazy. The car has m/t drag radials on it and has a full fuel system on it. I am going to mess with the load based timing table on it this weekend and see what happens.
 

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Q) What does turbo lag feel like?
A) feels like a natural aspirated car.

Lag is the length of time out of boost.

If a 351 can't spin the tires N/A in first gear. Your problem isn't turbo lag. At best it could be a mismatch of parts. At worst it could be a mechanical failure. Not enough information to know for sure.

Do you have a boost retard?
Your timing load table might need massaging?
Can you log fuel pressure?
Did you set base timing correctly? TPS?
 

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Discussion Starter #10
I can retard timing based on load vs rpm in moates qh. Right now timing is based on TPS WOT vs rpm, starting with 18 degrees of timing so when its running on motor it would be at 18 degrees total. I will switch to load based this weekend to account for the transition from motor to going into boost. Fuel pressure is fine, base timing set at 10 with spout out and I smoke tested the cold side for leaks.
 

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Keep ruling out the simple stuff first. If it's getting timing & fuel. A 351 should spin the tires in first gear regardless of boost or turbo lag IMO.
 

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the problem is your cam!
i did the same thing and i was like why doesnt it feel like explosive power.
get a f cam or custom cam all the boost ia leaking out on the overlap of that cam. my turbo cam made a huge difference.
call bob at cam motion
 

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the problem is your cam!
Could be? I hear what you're saying. But a Stage2 cam in a 351 should still spin the tires under atmosphere pressure.
The car feeling lazy has me thinking timing is off. As in the actual timing is not doing what the OP thinks it's doing. That's why I asked about timing retard.

But before I did a cam swap for his stated problems I'd do a compression & leak down to make sure the engine isn't hurt. But that's me. Running on 5 cylinders should still get the tires to spin in first gear??

But I'd still look at the timing first thing. Something isn't adding up. IMO it's not 100% the cam or even turbo lag. There's more to the story...
 
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Could add timing before it hits boost but until you change that cam no going to be good. My b-31 blower cam was doing th exact same thing. i was like this sucks why does it feel slow on bottom.
 

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I can retard timing based on load vs rpm in moates qh. Right now timing is based on TPS WOT vs rpm, starting with 18 degrees of timing so when its running on motor it would be at 18 degrees total. I will switch to load based this weekend to account for the transition from motor to going into boost. Fuel pressure is fine, base timing set at 10 with spout out and I smoke tested the cold side for leaks.
This makes sense now, it's all in your tune. Definitely switch to load based timing, and it's easier to work off of one spark table (sea level), and disable the altitude table. That way you know for sure what you're commanding. With that said, are you commanding 18 in your table or is it 8 in the table and you're adding the 10 Base to the 8? I think you just need to get the tune sorted out. You're sure fueling is correct? Get the fuel dialed in first, if you haven't already, and then sort out the timing. If you're commanding 18 in the table then that's 28 total, that should be plenty to get that turbine spooled if the fuel is dialed in properly. Check out efidynotuning.com if you haven't already, it helped me out a bunch when I was using the quarterhorse to tune my previous turbo build.

The camshaft isn't the best one, but don't sweat it. I ran a quick simulation with your heads (I have the same heads), the tfs stage 2 cam, displacement and SCR with the 7875 turbo (I used to have that turbo as well so I know the model is accurate-on the conservative side) and on 10 psi you should have somewhere near [email protected] RPM. The simulation says [email protected] RPM to be exact. That's assuming 1000cfm throttle opening, and a 60% efficiency intercooler on 10lbs and detonation free gasoline. I've run a simulation using the same turbo, and my simulation ended up being lower than the actual dyno numbers just for reference.
 

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Discussion Starter #16
As far as my cam I know its not the best but there are 2 well known builds on the turbo forums running this cam but with a s480 and they are in the 8's. This car was also lazy down low when I had the 331 in it with same heads, cam ,turbo and tune. I just didn't get enough time to mess with it bc I spun a cam bearing.

As far as the tune it has 18 total in the WOT vs rpm table. So that means as soon as the TPS voltage hits 3.8 volts it goes to 18 degrees total. Yeah I will be switching to sea level load based and already have the tune made for it with more aggressive timing in the NA area. Fuel is dialed in already and my wide-band confirms that.

I guess I could do a leak down test and a compression test to make sure every thing is on the up and up. Like I said the top end feels great but the bottom end is lazy.
 
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