Questions about boost pressure changes in my 850R and other performance related q's

[5280brick]

quick overview: 96 850R mechanically sound. mods- K&N, waste gate rod mod, hallman mbc and other bs free mods

Pertaining to turbo vehicles My volvo is the first and only A/T one I have ever driven. I am a former awd dsm owner so I have become addicted to acceleration. I have noticed certain things about the volvo that are much different from other turbocharged cars I've driven , #1 being the way the volvo builds and maintains boost pressure. For Example:from idle-
builds boost/ holds boost at set point/ A/Tshifts (at shift builds more than set boost point or "spikes"/drops/ holds /and so on with the repeating cycle as the car moves through the gears.
I have attempted to try and tone down the spike by lowering my set boost point to lower the spike point and have all new vacuum lines which are very short in length I have been all over the the air loop and appears to be air leak free. I just want her to build boost and hold the needle in 1 spot!

Has anyone been able to overcome this?

[Hoggster]

It's probably your MBC. The car has an electronic boost controller that reads off the MAF. there's no boost sensor.

[5280brick]

the mbc seems to be in perfect working order, I have used this here controller on my dsm and never had irratic boost spikes, I have bypassed the boost controll solenoid so the level should be dependent on the controller. Its almost as though when the car shifts gear the wastegate suddenly closes and then reopens a split second later but due to the pressure being at max set point when the wastegate closes the pressure reaches undesired levels then a short way up the rpm band the wastegate reopens and the boost drops back to set point for the remainder of the powerband in any given gear. as I rack my brain....

[Pennybridge Pioneer]

what's your downpipe/exhaust like? I have heard stories of spiking on elevated boost cars if their exhaust is too restrictive (ie. gas can't leave the wastegate housing fast enough) although what it sounds like MORE is that you are not experiencing boost "spike" but more like boost drop. Maybe your mbc is actually set higher than what you think, and it just drops boost (maybe the spring in the mbc is getting weak, it happens) really quickly, until you shift and all that load brings back the boost for a split second.

you could try going to volvospeed and having someone over there diagnose the problem, they're all into that fwd stuff. pretty much everyone over there that uses an mbc though experiences strange untraceable problems (and boost spikes at low rpms that turn conrods into con-elbows) the only way to get rock solid boost levels is to bypass the boost control solenoid completely and run an electronic boost controller with super quick response like any of the new ones out there from teh big names, the avc-r is really nice because you can control boost according to RPM and TPS which is great on the fwd 5-cyl so you get extra protection from bending those weak rods they put in there.

[volvo9]

I'd remove the MBC and see if it changes with only the wastegate rod adjustment. Me and my friend where running 18 Psi on his T5-R with no problems, and no spikes. We had a hard time setting the boost correctly with the MBC installed.

[Hoggster]

That's what I was trying to say. I'm sure your MBC is fine. Those cars don't like MBCs. It confuses the EBC and causes all sorts of crazy problems. Take it off and try another way to up the boost. I reccomend getting a chip, as the ECU governs fuel, spark and boost.

[volvorsport]

theres no problem fitting an MBC , ive sold plenty who are happy . when the gearbox changes the ecu detects it and alters the timing /boost to get a less harsh shift . What you are seeing is a result of that even though you have an MBC controlling the boost .

HAve you disconnected the electronic and just got the mbc i the control line otherwise that would nack things up aswell

[5280brick]

thanks for the input everyone. I have the mbc hooked up directly completely bypassing the bcs, I left the bcs plug connected and I am getting no ce lights or anything wrong. I am currently running stock dp/cat/ex and in the near future I plan to replace the mbc with a chip or new ecu depending on $$$.

Volvosport, what you describe about the ecu timing advance seems a logical answer!

Pennybridge, you are right on about a restrictive ex system causing backpressure and increasing boost but that happens a bit differently. My spiking is at low rpm when the a/t shifts and its for a brief moment. in a backpressure build up problem the boost pressure will start building normal and just keeps raising as rpm increases almost as though there is nothing stopping it from hitting extreme danger levels. I had a problem like this with my dsm. this problem is usually remedied by porting the wastegate hole next to the exhaust port on mitsu turbo's

[EricF]

Originally Posted by 5280brick

thanks for the input everyone. I have the mbc hooked up directly completely bypassing the bcs, I left the bcs plug connected and I am getting no ce lights or anything wrong. I am currently running stock dp/cat/ex and in the near future I plan to replace the mbc with a chip or new ecu depending on $$$.

Volvosport, what you describe about the ecu timing advance seems a logical answer!

Pennybridge, you are right on about a restrictive ex system causing backpressure and increasing boost but that happens a bit differently. My spiking is at low rpm when the a/t shifts and its for a brief moment. in a backpressure build up problem the boost pressure will start building normal and just keeps raising as rpm increases almost as though there is nothing stopping it from hitting extreme danger levels. I had a problem like this with my dsm. this problem is usually remedied by porting the wastegate hole next to the exhaust port on mitsu turbo's

So when you're going through the gears and it upshifts, the boost is higher in the next gear than it was before, but then tapers off?

If this is what you're experiencing, there are a number of reasons... My idea on the biggest reason is the turbine housing on the 15G's is pretty restrictive and usually creates a lot of dropoff on the boost as rpms rise, and these housings are also VERY prone to cracking.

What boost levels are you at?

There is a lot more to it than what has been said here, but these are a couple of ideas, and I don't feel real confident speculating further (though think about load levels and how they fluxuate when the car shifts maybe?)...

It's very difficult to get the 850s to hold a set boost level, especially with the stock turbo. On my car, I was running 20+ psi spikes, and it would taper down to 14-15 by the time the engine was spinning fast enough to shift. Many other people have experienced the same thing... Welcome to the circus

[Pennybridge Pioneer]

yeah i'd say you'd want to watch out for those low rpm boost spikes

[n xntrx volvo]

what boost you running? stock cbv? may not be able to cope, prop causing a lag in opening (spike) and having a hard time closing and not fluttering.

[5280brick]

I have it set at 13 psi and im hitting 15 psi spikes. Im playing it safe dont wanna go to lean with the stock ecu. I dont have any pressure drop though.

Question , how efficient is the fuel pumps in t5 cars? anyone switch out for larger pumps or does rewiring the fuel pumps in t5 cars help increase flow?

[EricF]

Originally Posted by 5280brick

I have it set at 13 psi and im hitting 15 psi spikes. Im playing it safe dont wanna go to lean with the stock ecu. I dont have any pressure drop though.

Question , how efficient is the fuel pumps in t5 cars? anyone switch out for larger pumps or does rewiring the fuel pumps in t5 cars help increase flow?

The stock pump, regulator, and injectors are good for a little over 300 horsepower with custom fuel maps (chip). 300 hp requires an upgraded turbo and exhaust at least though, and ignition would help a lot...

If you want to go any higher than that, a simple injector upgrade should suffice. I would suggest a fuel pump upgrade around 400 hp. Ask over on VS, one of the Swedes will know for sure. I wouldn't worry about the pump just yet though unless it dies, which is pretty rare.

[jpbturbo]

That's exactly the way my grainger valve mbc acts.

It will spike to about 15psi and then settle off at about 13psi, then when the tranny shifts it will have again a slight spike.
My thoughts are that the spring in the valve is not reacting fast enough(seems obvious I guess) and it allows to much pressure to build up before the ball moves backwards in the valve and allows the wastegate to open.
Normally when shifting on an automatic car there is a momentary loss in boost while the throttle plate closes.
On an auto car you don't let off the gas when it shifts but it's about impossible to get my car to make boost while it is in neutral. I would think that when the auto tranny shifts the engine isn't experiencing as much load and the boost drops off(on my 245 anyways) then as the next gear engages the boost comes back and you get a slight spike.

I think I might be rambling.

Peace,
Josh

[Boosted2003]

Originally Posted by 5280brick

thanks for the input everyone. I have the mbc hooked up directly completely bypassing the bcs, I left the bcs plug connected and I am getting no ce lights or anything wrong. I am currently running stock dp/cat/ex and in the near future I plan to replace the mbc with a chip or new ecu depending on $$$.

Volvosport, what you describe about the ecu timing advance seems a logical answer!

Pennybridge, you are right on about a restrictive ex system causing backpressure and increasing boost but that happens a bit differently. My spiking is at low rpm when the a/t shifts and its for a brief moment. in a backpressure build up problem the boost pressure will start building normal and just keeps raising as rpm increases almost as though there is nothing stopping it from hitting extreme danger levels. I had a problem like this with my dsm. this problem is usually remedied by porting the wastegate hole next to the exhaust port on mitsu turbo's

My conclusion to the whole td04 based turbos are the turbo flows more air then wastegate can handle. I know people think its funny sounding since the tdo4 dont flow that much. But its true. Try running at like 4 psi then smash gas. You should spike. I do that in my car with 3 inch turbo back. I have tired MBC. I had spikes of 20 psi when set at 14-15psi. Then once I put EBC. I dropped spikes down to 16-17psi(which is fine for the redblocks).

[5280brick]

How much boost are people running on t5's with stock motors?

Whats the cfm of the td04 15g and at what boost level does it peter out?

What are my options as far as larger turbo's? any other mitsu turbo's compatable like a td05?

Who makes good dp's for volvo's?

what vendors can I obtain a 19t from? who has the best deals?

seriously I wanna make my volvo quick, I wanna run with c5's in my box.

[5280brick]

.

[5280brick]

^up

[Boosted2003]

[EricF]

Originally Posted by 5280brick

How much boost are people running on t5's with stock motors?

Some people run over 20 psi on an untouched long block, but at that point you really need to be careful with your tuning.

Whats the cfm of the td04 15g and at what boost level does it peter out?

IIRC it's around 425 or so... Take those compressor maps with a grain of salt, as you can see they are very simplistic and I am very skeptical as to the accuracy of what's even there.

Most people observe that power gains past 16 psi or so are minimal... I've run up to 22 psi on the 15G and I pretty much concur with that.

What are my options as far as larger turbo's? any other mitsu turbo's compatable like a td05?

The DSM-type mitsu turbos aren't really compatible, as the Volvo mitsubishi turbos are based off a T3 flange and only turbos within this pretty small family will be a direct bolt-on. You can actually bolt on a T3 or T3/T04 hybrid with some minor machining to the manifold though.

The most popular upgrade is the 19T, though many of the Swedes are skeptical of them because they tend to build boost too fast for these motors to handle (bend a lot of rods). Many people have been happy with them, though many have also bent rods. I would suggest a 16T until you are ready to make close to 300whp, at which point an upgrade to a T3/T04 family turbo would be the way to go.

Who makes good dp's for volvo's?

ATR makes a pretty nice 2.5" downpipe for a very good price. There are a few 3" options (IPD, SAM, BSR, etc), but most are over $600... At which point I would recommend trying to find a shop to do one locally.

what vendors can I obtain a 19t from? who has the best deals?

Andrew Zizzo over at Volvospeed is a representative for BSR/Engstrom Motorsports, and I know he has sold a few 19T packages and people have been very happy with them. Though probably the most reliable source would be to go to Volvo directly.

seriously I wanna make my volvo quick, I wanna run with c5's in my box.

Well Charles at VS is in the 12s, and there are a few Swedes that posted recently in the 11s and 12s, it can certainly be done


Here's a basic article I posted at the beginning of the year about tuning these cars, just some decent general info:

http://forums.turbobricks.com/showthread.php?t=10961

Any further questions, I'll do what I can to help ya out

[5280brick]

Thanks for all the info, you know a price on the 19t?

I will probably opt for the 19t. my plan with the car is to make it quick and keep it as reliable as possible. the 19t is just a step up from the 15g in it and will probably be the friendliest choice. 300whp is a reasonable and respectable goal for her and that should be just enough power to put a smile on my face and blow many a v8's doors off.

[Boosted2003]

Yeah, The map is rough one I threw together. I have all the real ones. But when I put them together like layed so confusing you can't read it from all the lines.

[5280brick]

the chart still gives a good rough idea though. wow I cant believe the tiny turbo flows upwards of 500 cfm! thats about equal to a td05 16g. I want one!

how much is a 19t gonna run me $$$??? 500$? I hope!